Posting pictures.

Probably the wrong place, like everything else lately. I have been unable to post pictures when using the "start a conversation" mode.
Starting a conversation is not a problem, but when I try to reply and attach a picture, I get that small widow to "add photos" and it will not accept a "copy and paste." There is no displayed issue, i.e. "photo too big." I've been directed to the section on "Web site questions," but didn't have much luck with that. I know I'm doing something wrong.
Norm