Hi, David. Welcome.
Do you see the paperclip attachment option at the lower left of the reply window?
You can add pictures there, as long as they're small enough kilobytes. I think around 425 kb. Might be a little higher.
Or you can choose another host such as pinterest and post the picture address and the software usually automatically turns it into a picture.
You can also post in our gallery, and get the address from there to post in your threads.