Your avatar is the picture associated with your user account. Your avatar (or picture) will follow you around the community next to your forum posts to help other users identify you. Feel free to upload your own image according to the terms of service.
Navigate to your profile by clicking on the "My Profile" link.
Underneath your existing avatar, there is a "Replace Image" button.
Click the "Replace Image" button to pull up the Image tool. A popup will appear.
You can choose to upload an image from your desktop or import an image from an external URL.
When you are done, click "OK." Your profile will reload to display your new avatar.