Don't worry about asking questions, we all had to start somewhere, and I am by no means any expert LOL I have just had a little experience in some of these issues...that is all....really
!!
As for the CAB, all you do is save the entire file to your storage on the Omnia, and use file explorer to get to it and just click on it. You will see installation occur, that means it is working!!
You don't open the CAB file, or unpack it at all. Think of it like a program you place on your PPC ant run there.
See how that goes and let us know!!