I looked at the old post mentioned above and it seemed a bit involved. All I ever do is click on the paper clip on the little tool bar which brings up the "Manage Attachments" window. All you do there is select the file you want, in this case a picture, and then "Upload" it. The picture will be attached AND also show in your text box. Click the "Preview Post" button at the bottom to see what it looks like before you Submit.
Give it a try. It is easy once you have done it once.
Retired electronic technician (45 years in the field)
2017 Greyhawk 29W
solar & many other mods
wife (maybe I should have given her top billing)