Hello Phil,
You can choose the Owner for each Contact/Lead by placing that Owner's name into the Owner column next to the Contact/Lead in our ClickDimensions Import Template.
When importing new Contacts/Leads, the Backup Owner field will make the Owner of the Contact/Lead the User you select in the field. If no Owner is set in the Owner column of the Import Template, then the User specified in this field will become the Owner of the Contact/Lead.
If you have Contacts/Leads that were given the incorrect Owner, you could use a CRM Workflow to assign a different User/Owner to that record or do a Bulk Edit on those records.
ClickDimensions Import Tool: http://help.clickdimensions.com/import/
Are you still seeing the import behavior you expressed?