Can you describe what you mean by hasn't shed right?
If it's something like retained eyecaps, that can be quite tricky and dangerous for a new owner to try and tackle on their own (it's quite easy to blind your snake if you do it wrong).
If it's patches of skin that hasn't shed properly then that's easier to treat - if you wet a towel with tepid water (not warm to the touch as that would be too hot for your snake), and let him slither through it - it will moisten the retained skin and the act of slithering through it might be enough to shift it.
I think with corns the most common problem is with the tailtip - James our snake has had a few problems shedding right to the tip but the wet towel trick worked fine. There's a few pics of James' shed here: http://www.hencam.co.uk/hencam_forum/comments.php?DiscussionID=308
You can help him shed in the future by adding a damp moss hide when you notice your snake approaching shed (eyes blue, colour faded etc). There's a sticky on here on how to make a moss hide. We use a cheap tupperware container with holes cut in it (and smoothed so no sharp edges) with damp sphagnum moss in, and his last few sheds have been fine.
you could give him a shllow warm bath about the same temp as the viv then let him run through a towel while holding him and that should remove most of what is left and you can repeat this after a few days.