MOnStEr MuNCh - My First Time at Photoshop

So, we were given a brief for uni to basically re-design the Monster Munch brand to create it more appealing to students age 18-24. I have NEVER used Photoshop and Illustrator before, and so I thought that this would be a good place to start with this brief. Well, this is my first attempt at a Photoshop and Illustrator illustration.

I am struggling with this brief, and would really appreciate any advice, tips etc. Thanks.