I'm a bit of a noob with Forums, so could someone tell me how to post a picture? XD
First, find an image host that allows hotlinking. I use
Imgur or
Photobucket, personally.
Upload your image using the host (for photobucket, you'll need to register an account, which saves all your images to an album that you can make private).
Once you've uploaded the image, you'll be taken either to an image page or your album page, where you can find a "link for forums" option. Clicking the URL copies the image link (with appropriate forum tags) into your clipboard.
Paste that into your post, and you're good to go.
If you already have the URL of an uploaded image, just surround it with IMG tags, like this:
[img]http://image.url.com/image.jpg[/img]
But as Altoholic Monkey pointed out,
make sure you have hotlinking permission before you link an image. Hotlinking an image without permission is bandwidth theft, which is poor internet etiquette and will frequently get images removed or redirected to a placeholder.