Need help integrating wireless and wired networks

I just moved into an apartment that has internet shared through a
wireless network. I want to add two PCs and an XBOX but don't want to
buy a wireless device for each one since these devices are expensive
and the PCs and XBOX are in the same room. Is there a way to have these
3 devices exist on a wired network and connect that whole network to
the wired one? Thanks

I have a LinkSys wired router....

You'll want to look into a wireless BRIDGE. It'll take wired traffic,
and send it wirelessly.