There are a few ways to add up a column in Excel. One way is to use the SUM function. To do this, select the cells you want to add up, and then use the SUM function in the formula bar. Another way is to use the AutoSum function. To do this, select the cells you want to add up, and then click the AutoSum button in the toolbar. A third way is to use the shortcut key combination Ctrl+Shift+Enter.