How to utilize a wifi hotspot for a desktop pc and xbox?

Ok. I'm 32 and I wasn't intuitive enough to learn about computers when I should have, so now kids half my age get to tell me what to do. This is the situation: I have a 1. HP Pav. laptop with built in wireless card. 2. a free unsecured (yes I understand what this means) signal I am using. 3. I have a Gateway Desktop pc with NO wireless card. 4. an Xbox360 5. a Dlink wireless router. .........OK. So what I want to know is basically. How do I get the PC and the Xbox connected to the internet using the wifi signal? Is it possible? For 1 or both of the components? How in basic layman's terms is it accomplished? I thought the router would pick up the signal automatically but it seems, unless I plugged the ethernet cables in wrong, that this is not so. Anyone?