Trying to run iMovie on a 2015 macbook pro

Hi,

You won't be able to get the newest iMovie version until you update your OS. Howevever, try the procedure below to obtain the highest iMovie version that your Mac's operating system will run:

This procedure assumes that at one point in time you had iMovie on your Mac, even if you later deleted it. To update/redownload iMovie 10, drag your iMovie 10 app from the Applications folder into the trash, but do not empty the trash. (You can skip that step if you had iMovie 10 on your computer before, but deleted it.) Sign in to the app store and open your purchases folder by clicking on your name at the bottom of the app store side bar.   You will see your purchases displayed, including iMovie 10. Redownload/update iMovie from there. You will be given a prompt about downloading a compatible version. If not successful, drag your present iMovie app out of the trash (if you moved it there) and return it to the Applications folder.

-- Rich