TFS 2015 Access denied.

I am trying to Create New Agent pool. But I get an error saying "Access denied. User needs Manage permissions to perform action".

Can someone tell me. how can I add myself to "Agent Pool Service Account".

BTW I can't even see this account in TFS web portal,  where is it?  So that I can verify, whether I am part of it or not.

Any help is appreciated.