Outline of a shape

[rich2005]

Like I said very rarely that simple but.

Choose the color select tool
Click inside the shape to create a selection.
Go to a new empty layer
Use Edit -> Stroke Selection with a suitable line width.

30 second example: https://i.imgur.com/A73gAgZ.mp4

Can you post your image on http://www.imgur.com or maybe dropbox then post the link