Promote Standard User to Admin
You can promote a standard user to an Admin user directly in your Admin Dashboard.
Click on the Users menu in the Admin Dashboard, and turn your attention to the list of users (see below).
Click on Edit next to the user's role you want to change.
And click on Change Role to Admin and then Click to confirm.
Demote Admin to Standard User
You can also demote an Admin to a standard user as well, by clicking the same Edit button and clicking "Change Role to Member".