The first and most important step is to install the game. Then I found the "Rockstar Games" folder in my document, and there is a "User Music" under the "GTAV" folder. The specific path is: C: \ users \ your user account \ documents \ rockstar games \ gtav \ user music.
Then copy the music you want to add to this folder. This folder supports MP3 format, and other formats may be wrong. Don't use Chinese for music names.
Finally, enter the game. In the music settings in the game, select "Perform Music Quick Scan" to finish. So you can listen to your own music on the radio,
How to use:
Press Scan Music in Options Music first, and then select personal radio mode: continuous/random (no radio station can be selected).