Goss,
To find the wireless key, connect to the router via ethernet and browse to
http://192.168.0.1 (the default admin page). The DI 524 default user/pwd is admin/blank pwd.
I'm not sure how the screens look on that router, but I believe there is a Wireless button on left of screen. Under that you will be able to look at the wireless security and if it's using WPA, you are looking for the 'PreShared Key' (or PSK) which is a long string of letters/numbers. Copy this into notepad and then try to manually connect to the DLink wireless network. When it asks for the PSK, paste in the key you copied from the router.
HTH