You can do it two different ways.
1st way. If you have a picture saved on your computer you can click the attachments button in your reply or post window. Then choose file, located it and double click on it. That will upload it to the post after to hit the post button.
2nd way. I you see a picture on another site that you want to put on a post, Right click on it and copy "img url". Then go to your post and click the
button and paste address in between the two img tags. The cursor will default to where to past it so pay close attention after you click the
button. Feel free to do a bunch of testing in this room. We can always delete posts after you are comfortable with it. Hope that info helps and feel free to give it a try of two either way.