To add an avatar to your GoComics profile, you will first need to sign in to your account. After you have logged in, navigate to your "My Profile" page. Here you will see your display name and bio if you have added one:
Click in the center of the avatar box, and the upload dialogue box will appear:
Next, select "Browse," locate the image on your device that you wish to upload, and then select "Submit." If the desired image meets the avatar requirements, you will see a success message.