This page explains how to import data in the Reservation object using a CSV file.
Make sure that you do not attempt to write to the following fields, as these fields are set automatically by Booker25: B25__Start_Date__c, B25__End_Date__c, B25__Local_Start_Time__c, B25__Local_End_Time__c
To import the reservation times correctly, there are two options:
Use B25__StartLocal__c and B25__EndLocal__c, and use your user's timezone for each field
Use B25__Start__c and B25__End__c, and use the target Resource's timezone for each field
The first option is recommended if you are importing data for Resources in multiple timezones, because then you can apply the same timezone to every time field. If the Reservations you are importing are all in the same timezone as your user, then it does not matter which option you choose.