First prepare the InTrust databases in advance using the Providing Database Access document available here:
Focus on steps 4 and 5, substituting the SQL account for the Windows account (that would hold the dbo role) when assigning ownership of the database. The database creation scripts are available from the downloaded InTrust Full Package 11.0 installation media in the path ...\InTrustFullPackage_11.0\Scripts\Database Scripts.
Follow the InTrust default Installation detailed in the InTrust Deployment Guide available here:
Except for the following deviations from the default settings:
Specify Configuration Database:
Select the SQL Server and provide the SQL Account credentials
Select the InTrust_Cfg_DB database created previously
Then review and modify Default InTrust Settings on the
Automatic Configuration screen:
Select the Change Miscellaneous Default Settings (Optional) and here you can configure the
Default InTrust alert and audit databases using the databases created previously.