Hi there, posting a photo isn't very hard. You can go to this site and upload it:
After that copy the direct link, i.e. the link that looks like this: "https://i.pixxxels.cc/wjcr4nJ3/image.jpg", just copy and paste that when adding a new message.
Also, when writing a message, there is a "Tips & Tricks" link on the top right of the new post form, next to the topic input field. If you click that link it will take you to this page with an explanation:
kinkyforums.com/forum/?page=tools
Good luck and happy posting 