To enter a formula in excel there are five different ways. for the first method you first select the cell you want to add a formula in next you start with the equal sign and type in the formula. Another way to enter in a formula in is to type in the cell in the name box the enter the formula in the formula box and click enter. A different method is to select cell you want the while holding down control select the other boxes you want to use the formula with and where you want it to show and press enter. Another method is to select the row or column and click the auto sum button on the home tab. Another method is to open a dialogue box on the home tab ribbon in the formula section and type in the formula then press the OK button.