Converting Itunes on a Computer to a Macbook Pro using an External Hard drive

I recently brought a Macbook pro and I would like to access my old itunes library from it as I am planning on getting rid of my old computer (windows 7)

Before I could access all of my itunes library using an external hard drive, all of my music was stored there and none was on the computer. I would like to do the same with my new Macbook but I am struggling on how to do so.