Once you've completed the Rent To Own program for your D16 plugin, Splice will email you a copy of the serial number to the email associated with your Splice account. Your D16 plugins will continue to run with the Splice app open.
If you want to use your plugins without the Splice app, you can register your serial number by:
Input your serial number and choose an email to register.
Restart your DAW and relaunch your D16 plugin.
Normally, D16 allows their users to sell their serial numbers after they purchase the plugin. Unfortunately this is not allowed when purchasing through Splice rent to own.