wireless question

I a new to wireless stuff and I have a question. I have a D-Link wireless router, cable internet and a desktop. I want to move my computer to a room that doesn’t have a cable internet jack and wanted to know what I need to buy to make my desktop use the wireless connection. Right now the router is hooked to my computer, works fine and my wifi thing that I have works fine too… I just want my desktop downstairs and all the router and cable modem upstairs (where my connection is).

Thank you!