On the top right of the screen, it says "Signed in as: then your name"
Click on your name
On that page, there's several tabs. The 3rd one says avatar. Click on that tab.
Click on "Enable Avatar"
Where it says "Upload Avatar", click on browse and point to the directory/picture on your PC.
Then click "Save changes".
Not sure what Neil has it set at but the pic probably has a max of around 100x100 pixels.
Send me an e-mail with your pic if you have size issues and need resizing.