Step 1: Sign into your Office admin account via https://portal.office.com
Step 2: Navigate to Exchange admin center.
Step 3: On the left pane, scroll down and click More features.
Step 4: Click open under Permissions.
Step 5: Click Mobile on the left pane.
Step 6: Click the Add(+) icon respective to the Device Access Rules area.
Step 7: Select the device family, model and restrictions and click Save.