AD user attributes are stored in the tblADusers database table and AD computer attributes in tblADcomputers. Below is a sample report that lists users with no department and in a specific OU. (Highlighted part to be replaced.) The Lansweeper report builder is a SQL editor, so the below is standard SQL syntax.
If you only want to scan and pull certain OUs into your installation though, I would also double-check that your scanning targets are configured as such under Scanning\Scanning Targets and
delete any unwanted machines that have already been scanned.
Select Top 1000000 tblADusers.Username,
tblADusers.Userdomain,
tblADusers.Displayname,
tblADusers.Department,
'usersm.gif' As icon,
tblADusers.OU,
tblADusers.Lastchanged
From tblADusers
Where (tblADusers.Department = '' Or tblADusers.Department Is Null)
And tblADusers.OU = 'OU=TestOU,DC=TEST,DC=local'
Order By tblADusers.Username