That's one of my favorite models! That link will save you, but I just wanted to add that you can tell which fold you do first-- the one that doesn't change. The one that changes between valley and mountain does so because it was done after the primary folds that don't change.
That means you need to do the top part first and then push it down as you fold the layers back up and you'll end up with step 7. Another key thing is that you don't have to do everything at once. With these box pleats work from out to in. Alot of times when you go across all of the pleats you can flatten the model, and then open it up and do some more.
So do the top, flatten, do that very bottom, flatten. Now the middle part are just reverse folds which you can do once the model is flattened anyway.