If you purchased PitStop Pro 12 between February 2nd 2015 and the official release in April 2015, you don't have to do anything! They key you have received is also entitled to use PitStop Pro 13. Just download the PitStop Pro 13 installer for Mac or Windows and you're ready to go.
PitStop Server 13
If you purchased PitStop Server 12 between February 2nd 2015 and the official release in April 2015, you can exchange your product key for a 13 version by sending an email to containing your product key.
Connect 13
If you purchased Connect YOU 12, Connect ALL 12 or Connect SEND 12 between December 1st 2014 and the official release in March 2015, you can exchange your product key for a 13 version by sending an email to containing your product key.