In your admin dashboard, click on the Users tab. Next, click on the Groups tab and then under Groups. Select the group you wish to customize in order to match the header in Excel / CSV file. Next, select Import Settings tab and switch on Use group settings to enable matching of headers. Under the Date Format, select the format of the Date column in your Excel file. Then, match the headers by entering the customised header name and click save.
You can visit the tutorial page on How To Import Deliveries For Different Groups With Different Excel / CSV Templates.