You need two environment variable:
GOOGLE_SPREADSHEET_ID - The ID of the spreadsheet
GOOGLE_SPREADSHEET_RANGE - [name_of_the_sheet]![first_cell]:[last_cell]
E.g.
GOOGLE_SPREADSHEET_ID="1NypERxWOeG_VbfKmopOjGZyTDumZVKQfIjph5H60"
GOOGLE_SPREADSHEET_RANGE="Main Sheet!A3:F2000"
You can also update the majorDimension variable directly from the code ('ROWS' vs. 'COLUMNS')