A good link out lining how to get an iTunes Library from a windows computer to a Mac, is - MacWorld - Move an iTunes library from a Windows PC to a Mac
Also, when you got your new Mac and completed its setup procedure, it offered to migrate your data from your old computer. You can still do that, read here to learn how: http://support.apple.com/kb/PH4441. You many need to download "Windows Migration Assistant" on the Windows computer first - http://support.apple.com/kb/DL1557. Instructions are here: http://support.apple.com/kb/HT4796
How to move iTunes music to a new computer - http://support.apple.com/kb/HT4527.
iTunes for Windows - http://support.apple.com/kb/HT1364.