To add privileges you navigate the member’s profile page, then go to the privileges tab. Once on that privileges tab you will see the edit privileges button on the page specific nav bar. Click on that edit privileges button and the privileges pop up will appear. Make the privileges changes you’d like, then simply press save.
I was able to pull up your account and verify the privileges functionality is working properly. Which member are you trying to add privileges to? Let me know and I can continue to help.