Add documentation for instance setting to enable shared runners

doc/api/runners.md

@@ -448,7 +448,7 @@ Example response:
 
 ## List project's runners
 
-List all runners available in the project, including from ancestor groups and [any allowed shared runners](../ci/runners/runners_scope.md#enable-shared-runners).
+List all runners available in the project, including from ancestor groups and [any allowed shared runners](../ci/runners/runners_scope.md#enable-shared-runners-for-a-project).
 
 ```plaintext
 GET /projects/:id/runners
@@ -566,7 +566,7 @@ curl --request DELETE --header "PRIVATE-TOKEN: <your_access_token>" "https://git
 
 ## List group's runners
 
-List all runners available in the group as well as its ancestor groups, including [any allowed shared runners](../ci/runners/runners_scope.md#enable-shared-runners).
+List all runners available in the group as well as its ancestor groups, including [any allowed shared runners](../ci/runners/runners_scope.md#enable-shared-runners-for-a-group).
 
 ```plaintext
 GET /groups/:id/runners

doc/ci/runners/runners_scope.md

@@ -37,22 +37,31 @@ If you are using GitLab.com:
 - The shared runners consume the [CI/CD minutes](../pipelines/cicd_minutes.md)
   included with your account.
 
-### Enable shared runners
+### Enable shared runners for a project
 
 On GitLab.com, [shared runners](index.md) are enabled in all projects by
 default.
 
-On self-managed instances of GitLab, an administrator must [install](https://docs.gitlab.com/runner/install/index.html)
-and [register](https://docs.gitlab.com/runner/register/index.html) them.
+On self-managed instances of GitLab, an administrator can
+[enable them for all new projects](../../user/admin_area/settings/continuous_integration.md#enable-shared-runners-for-new-projects).
 
-You can also enable shared runners for individual projects.
+For existing projects, an administrator must
+[install](https://docs.gitlab.com/runner/install/index.html) and
+[register](https://docs.gitlab.com/runner/register/index.html) them.
 
-To enable shared runners:
+To enable shared runners for a project:
 
 1. Go to the project's **Settings > CI/CD** and expand the **Runners** section.
 1. Select **Enable shared runners for this project**.
 
-### Disable shared runners
+### Enable shared runners for a group
+
+To enable shared runners for a group:
+
+1. Go to the group's **Settings > CI/CD** and expand the **Runners** section.
+1. Select **Enable shared runners for this group**.
+
+### Disable shared runners for a project
 
 You can disable shared runners for individual projects or for groups.
 You must have the Owner role for the project
@@ -68,6 +77,8 @@ Shared runners are automatically disabled for a project:
 - If the shared runners setting for the parent group is disabled, and
 - If overriding this setting is not permitted at the project level.
 
+### Disable shared runners for a group
+
 To disable shared runners for a group:
 
 1. Go to the group's **Settings > CI/CD** and expand the **Runners** section.
@@ -78,7 +89,7 @@ To disable shared runners for a group:
 NOTE:
 To re-enable the shared runners for a group, turn on the
 **Enable shared runners for this group** toggle.
-Then, an owner or maintainer must explicitly change this setting
+Then, a user with the Owner or Maintainer role must explicitly change this setting
 for each project subgroup or project.
 
 ### How shared runners pick jobs

doc/user/admin_area/settings/continuous_integration.md

@@ -28,7 +28,18 @@ From now on, every existing project and newly created ones that don't have a
 If you want to disable it for a specific project, you can do so in
 [its settings](../../../topics/autodevops/index.md#enable-or-disable-auto-devops).
 
-## Shared runner details
+## Enable shared runners for new projects
+
+You can set all new projects to have the instance's shared runners available by default.
+
+1. On the top bar, select **Menu > Admin**.
+1. On the left sidebar, select **Settings > CI/CD**.
+1. Expand **Continuous Integration and Deployment**.
+1. Select the **Enable shared runners for new projects** checkbox.
+
+Any time a new project is created, the shared runners are available.
+
+## Add a message for shared runners
 
 To display details about the instance's shared runners in all projects'
 runner settings:
@@ -36,16 +47,17 @@ runner settings:
 1. On the top bar, select **Menu > Admin**.
 1. On the left sidebar, select **Settings > CI/CD**.
 1. Expand **Continuous Integration and Deployment**.
-1. Enter your shared runner details in the **Shared runner details** field.
+1. Enter text, including Markdown if you want, in the **Shared runner details** field. For example:
+
+   ![Shared runner details input](img/continuous_integration_shared_runner_details_input_v14_10.png)
 
-You can use [Markdown](../../markdown.md) for improved formatting. To see the rendered
-details:
+To view the rendered details:
 
 1. On the top bar, select **Menu > Project** and select any group or project.
 1. On the left sidebar, select **Settings > CI/CD**.
 1. Expand **Runners**.
 
-![Shared runner details example](img/continuous_integration_shared_runner_details_v14_0.png)
+![Shared runner details example](img/continuous_integration_shared_runner_details_v14_10.png)
 
 ## Maximum artifacts size
 

doc/user/project/settings/import_export.md

@@ -238,7 +238,7 @@ and the exports between them are compatible.
 
 ### Project fails to import due to mismatch
 
-If the [shared runners enablement](../../../ci/runners/runners_scope.md#enable-shared-runners)
+If the [shared runners enablement](../../../ci/runners/runners_scope.md#enable-shared-runners-for-a-project)
 does not match between the exported project, and the project import, the project fails to import.
 Review [issue 276930](https://gitlab.com/gitlab-org/gitlab/-/issues/276930), and either: