I have a friend with a Mac computer, I've never owned one. She says there is no way to upload photos from her computer files/gallery to a forum post. When I just tell her how I do it with windows 10, using the image icon, she says she can't do that.

There has to be a way for people who use Mac computers to upload their computer photos to an online forum or album. Any instruction that I may offer her to do this? Thanks.