So we’re going to start at the very beginning, a good place to start I’ve been told. Making a new document, and what you’re options are when doing this.
So open up Photoshop, click file in the top left corner and then click new. You’ll get a screen that looks like this
To start you can name your document. Under that take a look at the presets menu. I’ve pulled up the web preset, you can change the size to screen sizes like 1280×1040 or 1600×1200 – which means your image will be screen sized. It’s better to start off with a document that’s the right size than to try and change it later.
So that’s our very first lesson. Leave a question in the comments and I’ll be sure to answer it!