Hi,
First you need to know the wireless network's SSID, so you can connect to the correct network and not your neighbor's.
Then using windows (typically) or the native utility included with your wireless adapter, connect to your wireless network.
If you have wireless encryption setup thru the router (or access point) you should be prompted for the encryption key....enter it from your keyboard and press OK or enter.
All of this is predicated on the assumption that you have installed the wireless adapter hardware correctly in the first place.