How to prevent users from installing or managing add-ins?

Step 1: Log in to the Exchange Admin Console as a global administrator.

Step 2: Navigate to Permissions, and then select User Roles.

Step 3: Double-click Default Role with Add-Ins Management to open the edit window.

Step 4: Modify Default Role Assignment Policy by deselecting My Custom Apps, My MarketPlace Apps, and My ReadWriteMailbox Apps.

Step 5: Click Save.