This article will show you how to find what group a user belongs to. 

Instructions    

1. Navigate to Modules > Site Tools > User Administration
   
   
2. Select (and/or Search for) the user
   
3. Scroll down to Back-End Groups to view what internal groups they belong to
   
4. Scroll further down to Front-End Groups to view what public groups they belong to
   
5. To edit a user (including adding and removing group permissions), view our article Modify a User