I’ve been told that non Admins are unable to attach files.
So, I set up a new ID for myself with “member” powers.
I’m logged on here in member mode.
And it turns out I can attach files as a member. I’ll attach one now. Click on the thumbnail to see the window I see as a member.
The feature that lets you attach files is down at the bottom, after the “Options”, but before the “Preview Post” and “Submit Post” buttons. You can’t miss it.
If you are missing it, perhaps you are in “fast reply” mode.