How do i subscribe to games for windows live?

I bought Universe at war for vista and my buddy is getting it for the 360 so we can play together but I need GFW. Can I use the xbox live card code and put that in for GFW?

Do you have XBL Gold account? There's no reason to subscribe to Windows Live alone. The service is horrible for PC and only few mediocre games support it.

If you already have XBL account, you can use it just like you would use it on 360.