You can add user roles to your Community in the following steps:
1. Click on the Commerce tab on the left side bar.
2. Click on Community.
3. Click on the Community you want to edit.
4. Click on Settings on the left.
5. Scroll down on the general page and click on the drop down for Community Founder(s)
6. Click on the blue add button to select your users.
7. Create a new user and assign the user a role.
8. Watch the video below for more information.