Transferring music from pc to mac

I have just recently bought a Macbook Pro and am having a few issues with it.

I was a previous owner of a PC laptop and my itunes on my iphone 4s is synced with that computer. I am looking to move my itunes to this new macbook and transfer all of my songs over. I want all of my music to be on this new computer and be able to sync my phone here. I know that iphones can only sync with one computer so this is where im a bit stuck.

Thanks