Using item ID in CSV Import+

I’m trying to update records using CSV Import+ and would like to use the internal item ID assigned by Omeka as the identifier in the update process. The plugin manual says this is possible but I can’t figure out how to do it. The update action only seems to work if the identifier field is set to Dublin Core Identifier. Could someone enlighten me on how to use the internal ID as the identifier? Much appreciated.

In the bottom of the form, there is an option where you can set it.

I got it figured out. Thanks @Daniel_KM.