D-Link DAP-2590 - AirPremier N Dual Band PoE Access Point User Manual page 76

Section  - Using the AP Array
Step 2:
Set up the AP Array name and password. Click the Save button located on the lower right hand
side.
Note: Remember to select "Save & Activate". The AP will not become master until you select
"Save & Activate".
Slave AP Role
Click Advanced Settings > AP Array to view and edit the information on the AP in an array.
Step 1:
Click Enable AP Array and select the Slave role.
D-Link DAP-590 User Manual