You can't. He'd have to download the aIW version. And he can't just put the 10802 patch into his steam folder, he'd have to re-download the MP rip or Skidrow full game and then add the 10802 patch + update it.
Then if you want to do a private match, have the user you want to be host type "findexternalip" into the aIW console, then send the IP to your partner and have him type "connect iphere" and it should connect you guys.
Post in the MW2 Help section next time, as general is the incorrect section.