Click one of the checker links, run the checker and see the output.
Select and copy the text of the output table. Select it from the first (empty) cell to the last cell in the right bottom corner. Only the table content, without any textual information outside the border of the table. Like this.
Go back to this page and paste from the clipboard to the appropriate text box. After You leave the text box (click somewhere else), You can check the table on the right side. Filled cells are days with found.
Repeat for all challenge caches You want to have in Your calendar. You don't need to complete all of them.
Click the DOWNLOAD CALENDAR button section. The file with extension .ics will be downloaded.