This is how it works on a computer (I don't know what it's like on an iPhone as I don't have one). Using the new version of the forum, click on the thread you want to reply to/post on, and this is what appears:
Click on the blue Reply (at the right-hand side) and this window appears; click on the Plus sign towards the left and you get drop-down menu choices. Click on Image and a window comes up offering Drop images here or Choose images to upload. I usually use the latter, and navigate around the available sources to get the one(s) I want to put in. And that's it, really.
