CX Agent does not sync with Cisco's contract database.  When the CX Agent uploads the network data to CX Cloud, then there is a sync with the contracts database within CX Cloud.

When you go to Admin Data Sources and Add the data source for seedfile, you will be shown a screen to provide the file.  There is a template to download from there so you don't need to start from scratch.

It is IP range or seedfile but not both on the same Agent.  There is also CDP/LLDP for discovery now.  There is a template provided to download for the seedfile format.  The Agent docs linked from help give you lots of details.