So you have your characters and you want to outline them so after you cut out your png wich i have.

Now you will go to your right and right click on the png and scroll down to select > alpha to selection.

After you done that create a new layer but make sure you still have alpha to selection.

After you created a new layer which should look like this now.

Now you will select a color (i willl choose white) and you will use the bucket fill tool. make sure this goes onto your new layer so it should look like this.

Now after you done that we will go to. select > shrink

Click okay and then press delete so it should look like this now that you press delete.

You can see the white and what you do next is you go to. select >none   if you haven't. Click on the white (or the color your using) and move it around like this.

You can add more and make it like this. have fun with it.

There you go your done.

Sorry if i have typos :p

If you have problems feel free to leave them in the comment box below.

show me your result!