Hi Srini,
Quantum Spark Management application in Infinity Portal AKA SMP, It has replaced the legacy SMP when integrated into the Infinity Portal.
The admin guide that Tom has shared contains the relevant information on how to get started and connect the first gateway to Spark Management.
You have mentioned that the device is locally managed. Does that mean you do not plan to manage it in Spark Management? In that case, you will need to prepare in advance a plan and adjust the "Manage in SMP" for the relevant topics according to your preference. Note that the default "initial plan" has most features managed by SMP. Make sure that you enable cloud services like periodic backup to cloud, logs storage, statistics, notifications and more.
There is no requirement for having public IP address in order to connect to Spark Management.