The following guide might help you to configure Monitoring Plan, section "4.2.12. SQL Server":
I also attached the screenshot with list of necessary permissions for the data processing account.
In order to configure content audit, you should enable "Audit data changes" and configure rules per a certain scope e.g. server, database, table, column.
It is not recommended to use content audit against databases where information is changed by thousands of entries per second, for instance WSUS database, this might affect the entire SQL Server performance.
Just in case Netwrix Auditor 8.0 is not supported anymore, as well as documentation is related to 9.7, so I would recommend to update Netwrix Auditor to the latest version, there is no direct update to the latest version and if you have currently 8.0, you should update it following:
8.0 > 8.5 > 9.5 > 9.7
I believe much easier will be to remove current version and install the latest one, you may download it following the link: