Welcome to CF!
You'll just need a Wireless adapter for the desktop in order to connect to the wireless router. You can find one here
You'll need to install this inside the desktop which may therefore void any warranty on the machine. If you're not comfortable doing that, you can get a simple USB Wireless adapter such as this
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?