welcome aboard Mongo
The best thing you can do is to open Photoshop......... open a new document make it 500 by 500 pixels and start to click on the different tools to see what they do pencil first pick a size and have some fun
you see my thoughts are before you can create anything you need to get the feel of the brush first and I don't mean become an expert at it first just draw some lines and circles choose different colours add a gradient in then a new layer and paint some more etc
then go and start on Marks beginner tutes because they are so easy but remember if you get stuck just shout were here to help you along
but above all have fun
sfm