Do you want the PC to use the phone's internet? Or the phone to use the PCs internet?
If you want to use your PC's internet connection, you would need to create an AdHoc connection on your PC with a wireless adapter, preferably Windows7 or XP. (7 has a built in wizard). Unfortunately, Android hasn't added this capability in it's native stock form, to connect to an adHoc. So you would have to root your phone, and either install a patch file, or flash a custom Rom with AdHoc support.
In Laymans terms.