If you buy a license through DataGraph your registration information is automatically entered. If you buy through the web store you will get an e-mail from Kagi. Often this takes about 20 minutes. The registration information is at the bottom of that e-mail.
To start the registration, select “Register...” from the DataGraph menu
Type in your information and hit the “Validate Serial Number”
You will see that you are register either inside the about window
or in the DataGraph menu, in the grayed out menu item “DataGraph is Registered”