How
to Use Canvas Size Tool
Easy PhotoShop Tutorials
Now we are going to make the white background bigger by using CANVAS SIZE. Make sure that "BACKGROUND" is selected and not "BACKGROUND COPY" Once you have "BACKGROUND" selected, here's how to locate the CANVAS tool. Click on IMAGE in the top menu bar, and in the dropdown, click on CANVAS SIZE, and a screen is going to popup.
What you are seeing on this CANVAS SIZE popup screen is the size of your picture, which it says, my background is 4 inches by 2.64 inches.
I'm going to change it to 6 inches by 6 inches, to give me lots of room and then click OK. Enlarging the Background