If your Lansweeper database is hosted in SQL Server, it is fully open to external interfaces and you can insert data directly into the database. We can't really provide instructions or support for this, but
this forum thread discusses the required asset fields. Database connection details can be found in Program Files (x86)\Lansweeper\Service\Lansweeperservice.exe.config.
If these assets will be scanned at some point, you'll need to ensure that you submit all of the information we use to uniquely identify assets. Otherwise, new assets will be generated. More info on how Lansweeper uniquely identifies assets can be found
here.