This option enables you to set the access type to your device by choosing View or Modify. With Modify option, you will be able to add user groups who have access to this device and choose the access type for each of them.
To set the access type to your device select Access list in Row Actions buttons.
Or, click the Device Access List on the top right on the Details screen
You can start adding users or user groups by searching them in the Search users and user groups field. In the Access level drop-down menu, you can choose the access level for each user group.
After you define the access level click Add.