RE: How does the mix & match work?
That's all it is. You can just choose whatever section you want to do. It should just take you through that section, then back to the main menu (not all the way through the rest of the workout). At that time, you can pick your next section.
This is of course assuming that you didn't pre-program your workout ahead of time. I did that once, but it took longer to program it than it did to just mix and match manually.