If the software opened this help page, it appears that your calendar in the software is nearing the end and you will have to add more 'periods'.
Do not ignore this message. You will not be able to import into a future period if you do not perform maintenance.
All Treasury Software products have a built in calendar - called 'Periods'.
Periods are typically the end of each month. If you run the 'Periods' report, it might look like:
To add periods one at a time
Enter into an account (repeat for each account).
From the main menu, select Settings > Maintenance > Periods tab... then Add/Delete Periods.
To import periods
Choose 'Switch from Months to a Custom Period' tab and click the blue link to import your list.