Follow this guide if your site was created with the help of ITS. Follow the Change User Roles in a custom SharePoint Site guide if you created the SharePoint site yourself.
This article covers how site owners remove users from a SharePoint site.
Editing Users
Navigate to s.uconn.edu/sharepoint and click on your site.
Click Share in the top right corner.
In the popup toolbar, click on the carets to expand the groups.
Click on the permissions of the user you would like to edit and choose a new access level.