Hello and welcome Liz!
I'm still waving from a safe social distance behind the plague lines in the Seattle area.
The help section is full of good stuff (link below post), we love pictures but some of us have various issues posting. For example, I can't get the paperclip icon to work but others can. The most common issues are that once you choose your attachments and everything looks good, you need to extend the visible window to the far right corner to get to the upload button. The old board format was vertical -- now we are horizontal but that default window size was never changed.
The other issue is file size. It tells you something like 5MB -- but that is for all the possible attachments and is lower for just one. I have vision issues and can't see well enough for a smart phone, so I have an old school digital camera with limited software and my file sizes are just too large. I go to this site, use their defaults. and send it to my download directory. It's easy -- two clicks and a drag.
https://www.reduceimages.com/