Hi,
It sounds like you just want to set the device up as an access point
Internet -> Router -> Wired office Network -> DAP-1360 -> Wireless Network
If that is the case then just set it as an access point. The default IP Address is 192.168.0.50, you have to make sure that this is in the right range and free on your network, or you can change it by logging into the device.
BUT LISTEN UP... If this is rev A of the hardware (rev B should be OK) then you are going to have some serious connection drops and problems. I have a DAP-1360 rev A and it's so useless I use it as a paper weight. I'm serious you'll see others on this forum refer to this problem.
Anyhow if you have rev B, and if you need anymore help on setup, or I have miss-understood what you are trying to do, then let me know, I manage a network with 1 router, 8 switches and 10 wireless access points.
Good luck.