Welcome Leida, that is of course if you are not a spam bot. I apologize if I'm wrong, but we've been deluged with spam lately.
To set your avatar to display a picture which is hosted elsewhere, click on 'Profile' at the top. Then scroll down and at the bottom you'll see the avatar control panel. Look where it says: 'Link to off-site Avatar'. Type in the full address where the picture is being hosted, ie:
http://www.somewhere.com/pictures/somepicture.jpg . Please note the picture must be no larger than 100 X 100 pixels. Click 'Submit' to save the changes to your profile. Your off-site avatar should then display.