The "Authorization code" you’ve been issued is the licence number and registration code together.
The Authorization code looks as follows:
RL1000-0035-XXXXXX;XXXX-XXXX-XXXX-XXXX
The bit before the semi-colon - RL1000-0035-XXXXXX - is your licence number, and the bit after - XXXX-XXXX-XXXX-XXXX - your registration code.
Log in to your Reason Studios user account and point your browser here.
Choose the product you received Reason Lite with, and then enter your licence number and registration code as described above.