The same way you add photos to a regular thread entry. If you want to use a linked photo, use the little button on the top bar next to the smiley face mark, and if you want to upload your own, use the "upload a file" at the bottom of the text box. I don't know what the file size limit is, but if it's too big, it will show a broken picture on linked photos and give you an error message on uploads.
I just hit the "Upload a File" button down in the bottom right corner of the screen and select the image I want from the file manager.
That usually works, but sometimes the file is too large. My phone takes ridiculously large, Hubble Telescope level resolution pics that do nothing but burn through memory cards unless you're interest in figuring out the thread count on someone's shirt when they're in another prefecture, so I always have to scale down or I get an error message.
you can reduce the resolution on most phones you know .. that aside resizing only take moments with paint
I had forgotten about that part, thanks for the reminder. I tried recently to upload one image but it said it was too large or something so I had to scale it down.
