D-Link DAP-1620 Manual page 15

Push Button WPS Configuration
Note: You must have a WPS compatible router/access point
Step 1: Press the WPS button on your router/AP (usually for about 5-7 seconds)
Step 2: Press and hold the WPS button on the Extender for 5-7 seconds. The LED should
start to blink green. Once it makes connection with your router the LED will stop flashing