Here is how you can do it:
1. Go to for example www.photobucket.com
2. Register there and using instructions when registered upload your pictures.
3. Every picture then will have URL (link) for it. Select it and press Ctrl and C. That will copy it to clipboard
4. Go to ADVridder forum, reply to tread you want to, in new message window you will see above field where you type message an icon that looks like 2 mountains/cones ans sun on yellow sky.
5. Click that icon, paste (Ctrl and V) URL/link to photo, it will insert photo into message. Submit message. And that's it. Picture will show in your message.