I was really nervous at my first DSST too.
Actually, I like DSST's a little better. I dunno, I just like the screen better.
For your first one, you'll have to set up an account with a user name and password. You might want to jot it down on a piece of paper, because that's what you'll have to use to access your account later.
At my testing center you CAN print off your score right away....so just ask what the policy is there.
It's very much like a CLEP--you can mark questions, skip some, go back to some, etc. One nice thing is if you do the review at the end, the questions aren't simply numbered--they actually include the first few words of the question. I've found that helpful because some of the ones I've marked I decided I didn't want to bother going back to. So I didn't have to waste time clicking on them to find out what they were.
I don't know if it's a DSST thing or just the computers at my center, but occasionally when you click to the next question the computer will get a stuck and won't go. If that's a universal DSST thing, all I've had to do is simply go back a few questions and then try again and it works.
Overall, it's very easy and not hard to navigate at all. You'll do great!