adding a new laptop to my itunes account

See the following for instructions on authorizing a new laptop for iTunes: Authorize or deauthorize your computer for Apple ID purchases - Apple Support

Note that if you no longer have the old PC and already have 5 computers (not iPhones or iPads) authorized, you will need to use the instructions in the "If you need to deauthorize a computer that you don't have access to" section of that support article.