Gonna make this short and sweet. I see the question a lot, and explained a lot, but never a tutorial linked.
How to quickly post an image on the forums, using Imgur and CubeUpload. (I know there are more, but Imgur is the most popular, and CubeUpload is what I use). Any other service should be pretty similar.
Neither of these services requires an account, but it's definitely helpful if you ever need to access the links again.
Edit: CubeUpload currently requires registration due