john the ripper help

[kpmwrestler]

i had heard a lot about john the ripper, so i tried it out today, but i have no clue how to use it.
it can be used to crack encrypted files, not just linux account passwords, correct? i tried: "john-386 test.zip", but it said "no password hashes loaded" what does this mean? how do i crack a simple encrypted file?

 

[Osiris]

John the Ripper Tutorial

 

[kpmwrestler]

i tried that tutorial, and did exactly what it said but every time: "no password hashes loaded"

what kind of files can john decrypt?