First off, open the flyff folder. If you don't know where to find itthen click the start menu and search: C:\gpotato\Flyff. Then once yourin the folder go into the music folder and choose what song you want toreplace. Once yu kow what song you want to replace find a song toreplace it with and put it on your desktop and rename it with the nameof the song your replacing. I will be using: BgmDu1Mystery as myexample.BgmDu1Mystery is the music when you open FlyFF and your loggingin. I changed it to Session By Linkin Park. So copy BgmDu1Mystery andrename the song your replacing BgmDu1Mystery .
Hope this helps
And i will edit this soon to see if i have any errors.