Step 1
Once you have your graphic complete and you're ready to give it a border, simply go IMAGE - ADD BORDERS.
Step 2
A window like the one below should pop up. Just play around with the settings! I'm going to set my border to 8 Pixels White, but you can do anything you want. Once you've decided on your settings click OK.
Step 3 - extra step
If you want to give your image a double-border just repeat the steps as many times as you want! Hope this tutorial helped you!My final result:
