To upload your picture from your computer:

1) Click the "My Account" link on the left column.
2) Click Edit
3) Scroll down and you'll see the Upload Picture option
4) Click "Browse" to find the picture on your computer which you want to upload
5) Select the picture from your computer files
6) Scroll down to the bottom of the page and click "Submit"

Notes: Maximum picture dimensions are 120x120 and the maximum size is 30 kB

You can use a free photo editor such as http://www.webresizer.com to crop your picture and make it smaller.