how do i build a photo collage on my Mac

Hi

You can either get an app that will do it (perhaps from one of the photo printing sites) that plugs into photos. Or you can drag images from photos into pages and arrange them there.

Here is one I just did in pages in about 1 minute. It might need a little more time to arrange the images more nicely, perhaps with some rotations - but you get the idea...

You're welcome 🙂