A quick and dirty build guide for those that are interested. This is probably one of the biggest challenges of paper models; almost none of them come with build instructions so it's sometimes a lot of trial and error, especially if you've not done much previous model work. This is a fairly simple model as these go though, it's a slightly fancy box really.
http://imgur.com/a/LKjii
First pic, scoring all the lines. I used a live black Papermate finetip; a dead pen leaves good creases but a live pen gets rid of some of the white edges on the finished model. You can go over the edges again when finished, with a grey marker (because of all the white on the model, grey edging will look a bit better than black).
Second image, after cutting and folding. Note that the tabs around the canopy edge should actually fold OUT and not under, since they're going to be attached to the inside of the upper hull.
Glue the canopy together first. Then attach the front upper hull to the canopy area, using the details to align the piece. You can see that in the third image. Glue the side tabs together at the rear sides of the ship to create the back corners by the thrusters.
After that's set, glue the bottom hull to the rest of the ship, leaving the back open for last after you're sure you've got good seams. If you want to add any extra support to the inside of the model, in the form of extra card, cereal box, craft sticks; this is your last chance.
Keep the tabs for the back section slightly folded outward so you've got lots of contact area for when you do the final glue to set the back.
It took me about an hour or so actual build time from printout (yaaaay Scotch Quick Dry); the gf had Smallville reruns in the background so I got distracted by superheroey stuff or I would have had this up faster for people. Hope this is a help.