Board Thread:Support Requests - Community Management/@comment-26563820-20161129212301/@comment-24055022-20161129212822

Two ways that lead to the same page:

One, go to Special:UserRights on your wiki and type in the whole username, it'll go to their user rights management page, check the box for Administrator, and click save at the bottom.

Second: Go to the user's Contributions page, press User Rights Management, and do the rest as said above^.