Have a read through this post. It explains what you can do in the new forums and what trust level you need to be before you can do certain things.
As for linking to images, you can upload them to any hosting service, such as Imgur. It doesn’t really matter which. If your trust level is high enough, you can just drop the link to it in your post and it will appear inline. If the forum complains about you posting a link, try surrounding the link with backticks ( ` ) or use the preformatted text option ( </> button) so that the link looks something like this:
www.google.com