Reply to mac external hdd help

hi guys, I've just bought a macbook, and the issue I've run into is all of my music is now shred on a 2tb external which is obviously formatted for windows, i want to create a 1tb partition with mac format and transfer my music over, however when i go to utility to do this is says that it will delete the whole drive, I'm new to the mac world so go easy on me, i really haven't got a clue what I'm doing here