You're not alone - this flummoxed me too until I realised what goes on.
The coffeeshop software doesn't host images itself, but it's easy to link to a photo hosted elsewhere.
So... to include an image, first, upload your photo to a third party host. Postimages works well:
https://postimages.org/ - upload your image there and the site will give you a page of various forms of link to it. Look for the one that's a direct link and copy that. Then, go to the coffeeshop and the post you're writing, paste the link to your image. Lastly, highlight the link you've just pasted and then look above the editing field that you're using to type the post - the rows of editing icons that produce bold, italic typeface. With the image link selected, the one you need is in the second row, below the 'I' for italic script. Hover over it and you'll see the tooltip 'Insert image' - it doesn't actually mean that but when you hit that button it will turn the link you highlighted into something that results in displaying your image.
Hope this is somewhat helpful.
Mark
