When logged on visit your Profile
page. At the bottom you can find the section where you add an Avatar. Note that the "Show Gallery" facility is not implemented here at CameraLabs simply because that gallery doesn't contain any images. So, what you need is a publicly accessible image (one that you can share the URL of with a friend and that he/she can put into their browser to see the image). Then, and most importantly
, check that the avatar image complies with our stated size restriction:
...its width can be no greater than 80 pixels, the height no greater than 80 pixels, and the file size no more than 6 KB.
Then, and only then, you can put that URL into the "Link to off-site Avatar:" edit box and click the Submit button.
P.S. I'm not at all sure why you originally put this thread in the Nikon section.