The Edit List Permissions allows you to easily modify permissions on SharePoint Lists in Office 365.
Fig 1. Click Image to enlarge
To use the Edit List Permissions, you must first select the Site Collection, Site Name, and the SharePoint List name. Clicking the Get Existing Permissions button will retrieve the existing permissions on that List.
Once the existing permissions are displayed you can either Add/Remove users or if a list has custom permissions set, you can reset the role inheritance so that the existing permissions set at higher levels are replicated down.