When you first launch photoshop, you’ll need to open a new blank canvas. To do this, click on file, then select ‘new’.
Next, from the new document dialog box, select the type of media you want to create. In this case, I’m going to create a document for print, so select ‘print’ from the list at the top.
Then select the size. I”m going for A4 landscape.
Click create to begin.