Add specific location for enforced group 2FA

doc/security/two_factor_authentication.md

@@ -39,8 +39,9 @@ period to `0`.
 
 If you want to enforce 2FA only for certain groups, you can:
 
-1. Enable it in the group's **Settings > General** page.
-1. Optionally specify a grace period as above.
+1. Enable it in the group's **Settings > General** page. Navigate to **Permissions, LFS, 2FA > Two-factor authentication**.
+You can then check the **Require all users in this group to setup Two-factor authentication** option.
+1. You can also specify a grace period in the **Time before enforced** option.
 
 To change this setting, you need to be administrator or owner of the group.