If you have the picture as a link (ending in .jpg or .gif or something along those lines), all you have to do is click on this icon in the reply box:
and paste your link in the pop-up box. If you don't want to do that, you can go down below the reply box (when you're doing a regular reply, and not a quick reply), and click on Manage Attachments. There will be a pop-up, and you can upload your pictures straight to that. There is a limit of 5 pictures when you use attachments, and 10 pictures if you use the link form.
I hope that helps, and I can't wait to see more pictures! You've got some very lovely snakes.