When you log in to MyCompass, click on the 'Welcome' menu at the top right of your screen:
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Click on "Account", which will take you to the Profile Edit screen:

You can then click "Upload Image" to select a photo from your computer. 

Tip: Log in to MyCompass on your phone to upload a profile photo you have taken with your camera.

Your profile photo then is displayed whenever you make a timeline post, or make a comment: