Instructions
Click on the "Start" button in your taskbar, and then click on the "Documents" shortcut in the Start menu. Open the "User Files" folder, and then open the "GTA: San Andreas User Tracks" folder inside of it.
Open the folder containing the audio tracks you'd like to import into "GTA: San Andreas." Hold down the "Ctrl" button on your keyboard while clicking on each of the desired tracks. Right-click on the selected tracks and then select the "Copy" option from the context menu that appears.
Right-click inside of the User Tracks folder, and then click on the "Paste" option in the context menu that pops up. Close the User Tracks and music folders, and then launch "GTA: San Andreas."
Open the "Options" menu from the start screen and then open the "Audio Setup" menu. Select the "User Track Options" shortcut to ensure the "Automatic Media Scan" is set to "On." Select the "On" option if the Automatic Media Scan feature is toggled off. Exit the User Track Options menu and return to the main menu.