Jhansenku find your ST3 folder, go to settings, info, show stage traxx 3 files, make sure the replacement song titles are the same , place your updated song in to it and overwrite the old one, then go to SONG mode and resync your folder by a swipe down on the list , to be sure to be sure, and it’s done.
The thing to watch out for is if you have changed the tempo or added/removed audio , your text editor will need fixing to suit your changes , if it’s tone/balance change you should be fine.