Hey
@subconscious.
You do this in the same way that you post a picture to the forum:
1. First create an Imgur account.
2. Then upload your chosen image to the site.
3. Go to the images tab. Top right of screen.
4. Click on the image you want to upload. You will be given a series of links that you can copy.
5. Copy the link that says "direct link"
6. Paste this into your profile description in the 'biography' box.
Hope that is clear and helps.