Hi Writermom . . . I notice you have a picture on your profile.
If you can get one to upload there you should be able to get it to upload to the avatar area as well. Usually the only thing that would prevent it would be the pixel count of the picture, but the same size restrictions pertain to your profile picture as well; and the system will usually tell you if size is the problem.
Since you haven't been a member long enough, you can't have a signature yet so if you were trying to upload a picture to your signature that's why that won't work.