Connect your PC/Laptop to the router using a network cable.
First click start, then run, then type cmd and press enter.
Type ipconfig /all at the prompt and press enter.
Look for the entry relating to DHCP server and take a note of the ip address, for example 192.168.0.1
Type this into your web browser, e.g
http://192.168.0.1 and press enter.
This should bring up your router configuration page, the default username/password for a belkin router is ( as far as I know) admin/admin.
Depending on how it is set up, it will either have menus down one side of the screen or tabs along the top relating to security, look for wireless security and select WPA, you might get the option to autogenerate a key or have to manually type one in, if so it 26 characters long and can be from 0-9 and A-F so pick numbers and letters at random.
If WPA isn't supported, select WEP 128 bit, the rest is the same.
Once you have done this - scan for wireless networks and enter the key above when prompted, you should only do this once.