Go to the Settings tab on the top tool bar.
On the left hand side under My Settings click on Edit Avatar
Then check the box Use Custom Avatar
Then enter the URL address if the picture is on the WWW under Option 1
Or click on Browse on Option 2, find it on your computer/phone and follow the instructions
Then click on Save Changes
If your picture is too large to load just email it to yourself which will resize it and then use the resized picture.