To reference an empty cell in a formula, you can use the ISBLANK function. Here's how you can write the IF statement to return one value if the cell is empty and another if not:

1. Start by typing the equal sign (=) to begin the formula.
2. Type the IF function, followed by an opening parenthesis.
3. In the first argument of the IF function, use the ISBLANK function to check if the cell is empty. For example, if you want to check if cell A1 is empty, you can use the formula
   Code:

   =IF(ISBLANK(A1), "Value above", "Value itself")

   .
4. If the cell is empty, the formula will return "Value above". If the cell is not empty, the formula will return "Value itself".
5. Close the parentheses and press Enter to complete the formula.

Note that you can replace "Value above" and "Value itself" with any values or formulas that you want to return based on whether the cell is empty or not.