If you have purchased a Digital Download from this site, you can find all of your purchased downloads from the tab at the top titled Manage Account->MyAccount (here). You may also find them under the Manage Account->Orders page, by clicking on the individual order page.

You will see a list of the items that are available to be downloaded. Just use the right mouse button click and choose- Save Target As . A folder browser should pop up and you can choose a folder in order to download the image there.

You can then find the Image in that folder on your browser, and either print it or open it up into a photo editor and use it in your digital art. For more help on using digital downloads in Photoshop, you can find some tips on the Using Digital Downloads page.