There are a few ways to add in Excel. One way is to use the plus sign (+) between the numbers you are adding. Another way is to use the SUM function. To use the SUM function, highlight the cells you are adding, and then go to the "Formulas" tab and click on "SUM." A third way is to use the AutoSum function. To use the AutoSum function, highlight the cells you are adding, and then go to the "Formulas" tab and click on the "AutoSum" button.