how to use Apple music into iMovie?

Hello,

I am using a 64gb,iphone6 with 10.2.1 IOS.

I just recently bought apple music so i can play it offline and also use in iMovies.

I downloaded few songs, but when i go to iMovies to upload music in it, All the tracks i downloaded in music library are not able to select or upload( they are shown in fadded black letters ). what is that means? how can i easily able to use music tracks in iMovies.?

Any suggestions?