How do I merge two separate itunes accounts on the same computer?

I set up a new account on my Mac computer. The original account (that still exists) has all of my itunes music in it (it is a shared computer, but I decided to set up my own account), but the new one doesn't. How do I transfer the music from my phone to the new itunes account or merge the two?

Basically the itunes library on the new account is empty, so I can't sync it with my phone or else it will delete all of the music on my phone.