For 7.3
Register now link is enabled/disabled using :
Go to System admin-->Then select --> User Admin UI Tab-->Enable self registration link Save it.
Assign the UME action UME.Selfregister_User to a role assigned to the group anonymous users.
You must assign this action or no users can register.
Restart server.
Users logged in through self registered link will be automatically assigned "authenticated user" groups.