This really is as simple as it appears. When CalEventer is launched, the name of every calendar in your Calendar Store appears in the table on the left side of the main window. You can check as many calendars as you wish using each desired calendar's checkbox:
Clicking on the column headers (entitled Calendar and Use) will sort each column, initially in ascending order. A second click will re-sort in descending order:
It does not matter whether or not Calendar is running when you are using CalEventer, as the application derives is data from the Calendar Store Server on your machine. Feel free, however, to run Calendar and CalEventer simultaneously; any changes you make to any Events are registered in your root database, and as long as you have finished all of your edits before you click CalEventer's Go button, you will have no problems. The Refresh Calendar List button is only necessary if you create a new calendar or change the name of a calendar after you have launched CalEventer.