Creating a new document in Photoshop is great, you got so many options to suit everyones needs.

To create a new photoshop document go File > New...

We are going to name our document, by default it is Untitled-1, you can change this to what ever you want, ive chosen Portfolio Layout.

Preset is the size of your document, you can choose from sizes for postcards, website layouts, to paper size.

If you want to create a custom size document you can choose from pixels, inches etc.

Background contents is the colour of your background, you can choosing transparent gives you no background colour so you can place your document into anywhere with different backgrounds and it will change accordingly.

When you have finished choosing your options, click OK. You should now have this:

If you would like more help with this tutorial please register and visit the forum.