Ok wired should be fine without the wep key.

You need to make a new connection and go through the new connection wizard. The first page asks you if you would like to set up wireless or wired.

As you are able to "hard wire" the ps3 i would go that route as not only is it easier to set up but you'll also benefit from a better connection. To start with a would allow the ps3 to do this automatically just to try and get connected. Again from memory this is in the network connections menu on the ps3

the first page as above ask's you if you would like to set up a wireless or wire connection. Once you get here you are in the right place