To add an avatar to your profile, click on "User Control Panel" in the upper left corner of any forum page. then, select "Profile", then "Edit avatar". Animated avatars are not permitted.
There are three methods that you can use to add an avatar to your profile:
1. To upload an image from your computer (Upload from your machine)it must be 128 x 128 or smaller, with a maximum file size of 6k. Just click the "Browse..." button and select an image from your pictures folder or another location on your computer. Then, click "Submit".
2. To upload an image from a website (Upload from a URL:) it must be 128 x 128 or smaller, with a maximum file size of 6k. Just copy the entire URL of the image (http:...), found in the address bar at the top of your browser, and paste it in the box marked "Upload from a URL:" on your User Control Panel. Then, click "Submit".
3. If you want to use an image that is larger than 128 x 128, and 6k, as your avatar, you can link to it (Link off-site:). Just copy the entire URL of the image (http:...), found in the address bar at the top of your browser, or the "http..." link on an image hosting site, such as Tinypic.com
(Those links are usually titled "Direct Link" or "Direct Link for Layouts"), and paste it in the "Link off-site:" box on your User Control Panel.
If you use the "Link off-site:" option, because the image you want to use as your avatar is larger than 128 x 128, you may also have to change the "Avatar dimensions:" on your User Control panel to 128 (or less) x 128 (or less). And, if your image is a common image size (eg. 640 x 480, 800 x 600...), or any image that isn't square, it will be distorted unless you adjust the ratio of width to height. The image actually remains the same size, so the forum software stretches or squeezes whichever dimension it has to, and as much as it has to, to make the image fit in the avatar dimensions that you specify.
Here's an example:
Image size: 587x316
For instructions on how to upload images to an image hosting site, see How to post images
The early-bird gets the worm, but the second mouse gets the cheese.