How can I get music from my itunes or apple music to work in imovie?

iTunes music should play fine in iMovie. You need first to download the songs from the cloud into your physical iTunes library. iMovie won't read songs that are in the cloud.

As for Apple Music, the songs from there are all DRM protected and cannot be used in iMovie or any other application. Downloading them to iTunes will not remove the DRM protection. Further, Apple Music is a subscription service that gives you a license to listen to the songs for personal use for as long as one keeps the subscription current. So they cannot be downloaded into an app, where they could then be played after one cancels the subscription. In other words, you are renting the songs, so to speak, but do not own them.

-- Rich