Go on your profile in game as you would to chose a image head thing… And there should be a button to take you to the old forum. Here you can use a link to an image.
If you want to use your own image you’ll need to go on an image hosting website such as imgur or others (there are numerous)
Try to use square images and put 200 x 200 in the size area (or leave this blank if the image is smaller than this size)
If you need further explanations just say