How can I give a new user only Admin Rights to one DNN portal?
Currently, we have two portals but I only want to give the users rights to the one portal on DotNetNuke.
What you've described, is in-fact how the "Admin" role works within DNN.
If you are used to the "Host" role, which does span DNN portals, I can see why you'd be confused.
Setting up an Admin user, or any other security role, will only be honoured on that specific portal.
If you want a user to have admin access over multiple portals - They will have to have separate admin accounts.