Edit new version text and add a link to setting

doc/administration/auth/smartcard.md

@@ -4,12 +4,18 @@ type: reference
 
 # Smartcard authentication **(PREMIUM ONLY)**
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/33669) in GitLab 12.6,
-if a user has a pre-existing username and password, they can still use that to log
-in by default. However, this can be disabled.
-
 GitLab supports authentication using smartcards.
 
+## Existing password authentication
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/33669) in GitLab 12.6.
+
+By default, existing users can continue to log in with a username and password when smartcard
+authentication is enabled.
+
+To force existing users to use only smartcard authentication,
+[disable username and password authentication](../../user/admin_area/settings/sign_in_restrictions.md#password-authentication-enabled).
+
 ## Authentication methods
 
 GitLab supports two authentication methods:
@@ -88,10 +94,7 @@ Certificate:
 
 ### Authentication against an LDAP server
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/7693) in
-[GitLab Premium](https://about.gitlab.com/pricing/) 11.8 as an experimental
-feature. Smartcard authentication against an LDAP server may change or be
-removed completely in future releases.
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/7693) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.8 as an experimental feature. Smartcard authentication against an LDAP server may change or be removed completely in future releases.
 
 GitLab implements a standard way of certificate matching following
 [RFC4523](https://tools.ietf.org/html/rfc4523). It uses the