Put the jeansdenim file into player.img in your GTA San Andreas folder.

player.img file can be found in models folder in the GTA folder.
To import the txd file into the player.img file easily, you can use TXD Workshop app to import it to player.img.
TXD Workshop download link: https://www.gtainside.com/en/sanandreas/tools/12124-txd-workshop-4-0/download/
TXD Workshop is made by a cool user, but not me.