First go to some image hosting service, for example: imageshack.us/

Then click browse, and add your files (you can add multiple files at once, by pressing Ctrl and clicking the files one by one, or clicking Shift and selecting files from X to X.

Click "Upload Now"

When it's done uploading you should see the miniatures of your pictures, with a box of links on the right "Get links and Codes for All Images".

Then you simply click inside the box with links, notice they will al be selected at once. Press Ctrl+C.

Finally create a new topic here at kinkyforums, and Ctrl+V the links into the message box.

That's it!