Thank you so much Aga and Marilyn, I got your answers.
It fairly easy Marilyn. I will help you. In the upper left corner you see a link that say "user cp". You should click that and once you get there you have a menu at the left. Click on "edit avatar". There you can pick an icon that's already a standard on FF or you can pick your on icon. To do that you click on "use custom avatar" and then you have two options, to put in a link to the icon or if you have one saved on your computer you click that and after you are done you click "saves changes" and you have an icon.
I hope that was helpfull. If you have any more questions don't hesitate to ask.