When you are posting a “reply” to a thread, there is a second box under the one you type in. In it, it has a “Attach Files” box, with a “Manage Attachments” bar in it. Click on the bar, and find your pic. It will be listed, once you “attach” it. You may not see it in the “reply” post, but it will come up in your post, if it is listed. You can take it right off of your computer, you do not have to have it “hosted” by someone else. They “host” pictures right here.
Go to the “Test” forum, it is close to the bottom of the list of forums, and try it out. That is what it is there for.