type in your WEB address for your router 192.168.1.1 should be the safecom home page
On your security page click on WPA and then there should be a PSK or Personal Security Key button click on this. You should now see a section where you can add your security key, this must be more than 8 characters long and no more than 64.
Enter your character string or password eg. 'pcbobby_1234' click apply then start up computer log onto your router as usual, you will now be asked for your password key, type in pcbobby_1234 and if there is a tick box to remember password tick this, you will not be asked to enter your key again.
WPA-PSK is far safer than WEP, WEP is poor/broken security.