Can't not add ad azure account to gitlab?

I have installed Gitlab 8.15.2 on ubuntu 14.0 server. For my gitlab, i use ad azure like authentication provider.
When i click on the azure button on the welcome page of my gitlab and i login with my ad azure account. My ad azure is created well on gitlab with the status blocked. It’s ok for me.
But now if i am admin and i want to add an ad azure account to my gitlab by using admin portal. How can i do it ? I spent many time to find it but i did not succeed :frowning:
Could you please help me to resolve it ?
Thanks in advanced,
Best regards,