You sign up for an account, choose black or white layout, serif or sans and then begin uploading your work as you please. You can drag and drop and reorder things, tag stuff, and all sorts, and in the end you'll have an online portfolio at .carbonmade.com. You can even add video, but that costs an upgrade - I think it said fourteen bucks but as I just went to re-check it now reads "Howdy! We're currently revamping our paying plans! Stay tuned!". Anyway its still pretty interesting.
Check out some of the kids that already show their stuff off here. Like Andre the illustrator at in7es.carbonmade.com.