Granting User or App Permissions

I've recently created an app that is currently in sandbox. When I try to use this app and the credentials generated to make a phone call, I get:

"In order to call this API endpoint, one of the following permissions [RingOut] have to be granted to the authorized user."

I have seen other questions similar to this, and the general answer is to log-in to the admin portal and grant that user the proper "Role" for that permission. However, I'm a bit confused here - when I log in to https://service.devtest.ringcentral.com and look at Users, I only see myself (super admin) which is the same number/username I'm trying to issue my call from and getting this permissions error. How do I grant my specific app or clientID "RingOut" permission? It already is added as an application scope.