iPhone 8 Plus custom ringtone setup?

[KeThomas91]

So I know I have to use garage band and I have figured most of it out except there are only like 3 songs I can pick from on my downloaded music in iTunes.
Most of the other songs are all “greyed” out. Can someone tell me why that is and if there is a way to change it so I can select the song I want? I’m new to the iPhone 8 Plus coming from a iPhone 5 and I have never used garage band before now
Thank you

 

[Minorite]

Garage Band is an option, but better use iMazing for ringtones (>guide<). Much easier, used by a lot of people here and ringtones management is free, so no need for license.