I can't really say regarding a level graphics, but for gcse graphics we were doing editing on photoshop mainly & 2D design, we developed our initial design ideas in our sketchbooks
- this could be a basic design you don't have to be great, just put enough effort into it, as the majority i think is done on the computer. I think you make a product as well to do with advertising also
If your school has a computer system it should have some software on their called Photoshop/2D Design - play around on these or perhaps watch some youtube tutorials may help?
most of the skills will be taught though and teachers will give you advice on your projects - there will be some people who will be in the same situation as you - in our a level design class people came from technology and art from post gcse.