delete music library..

i have some 800+ songs in music library..but no songs in iphone 5s.

i want to delete music library and create nee music folder which i will sync or copy to iphone 5s.

how to do that?

i cant locate music library in itunes.

i have windows 8.1 os on my laptop.

also can i have any application thru which i can lock that app like whats app or vdo's.\