Within each Criteria Set, there is an 'Advanced' button.
Clicking on this leads to a new window with two tabs. The second tab is called 'Collation'.
It is automatically set to the default setting that is pulled from your Windows regional settings. If you want to change the Collation settings within Importacular, the window points you to a Microsoft Page that provides you with a large table of Default Collation to choose from:
Select and copy the Default Collation that you need and paste it into the available field back in the Advanced Collation setting in Importacular: