How do you transfer your itunes library from one computer to another??

I recently purchased a new labtop and need to transfer my itunes library from my old computer to the new one. I put my itunes library onto an external hard-drive. I thought I could simply connect the hard-drive to the new labtop and drag the song library into the 'My Music' folder or into the itunes program and the song would be there. Unfortunately that is not working...I am wondering how I upload my itunes library from the external hard-drive onto the new labtop.???