Open a new file by clicking on FILE --> NEW.

Color the background by using your FLOOD FILL TOOL which is located to the near bottom left of your screen.

Using your TEXT TOOL, write in the words, phrase, or sentence you want bordered.

Go to SELECTIONS ---> MODIFY ---> EXPAND.

Adjust the number of pixels you want it to be. The higher the number, the thicker the border.

AND YOU'RE DONE!