@sebastia.net 

You do not need to change any configuration. I would recommend factory defaulting the extender first by holding the reset for 15 seconds after it has already booted up. 

The only thing to worry about when adding a second extender is to not connect it to the existing one. Daisy chaining extender will kill your speed. If both the extender and router have the same network name, you could either unplug the existing extender, configure the new extender then plug the first back in. The other thing you can do is to look at the MAC address to determine which device is which. The sticker label on the extender should tell you the MAC address.