How do I open port 22 *SSH* to selected machines only? *I.E So only they can SSH in* on Win7?

One thing I like *Yet has me cautious as well* about Ubuntu is that port 22 is open. This may also be a problem too since someone can brute force into that port as well *Guessing, I don't know much about ports and only know basics of SSH* so I want to know, how do I make it so that my devices can SSH into my Windows 7 box? I can always do it the hard way and do it from Ubuntu and search the partition that it's on, but I want to know how to open SSH port. I understand this may be dangerous, but I just want to make it a bit easier.