I have heard that some people are having problems changing / uploading a new image for their Avatar / Profile picture.
On the screenshot image below there are
3 red circles labelled 1 to 3.
Firstly, you need to delete the current/existing image by clicking in the box
(red circle number 1) and then pressing the Delete button
(red circle number 2). When the page has reloaded itself you can then upload your own image using the 'browse' button
(red circle number 3) and choosing an image on your own computer and then clicking the 'upload' button.
Alternatively, you can delete your current image and then choos one of the pictures supplied instead of uploading your own image.
If you are still having problems or need more help then write a message in here and I will do what I can.
Cheers
Chris