that makes life easy, I've got one of those in the cupboard :)
You have to do this with a computer that is connected to the router using an Ethernet cable, then simply click the link below (or open your browser and type the address below into the address bar and hit enter)
http://192.168.1.1
This should take you straight to the admin pages for the router. Once it's loaded click on the word wireless in the grey bar along the top.
In the first page that comes up all you need to do is change the wireless network name (SSID) to what ever you want it to be, this is the name that your network publicly broadcasts so you can find it and distinguish it from other peoples networks.
Then click on the word security in the dark grey box on the left hand side (not the light grey bar along the top)
On that page there should only be two things to change. first select WPA-PSK/WPA2-PSK from the drop down menu next to security mode and then the only other option should be the WPA Shared Key, just type whatever you want in there as your wireless password/key. you can put what you want as long as it's between 8 to 63 letters/numbers
Once that's done, select save settings go to the laptop and you should now be able to find and connect to a wireless network called what you set in step one and using the key you set in step two.