1. Activate the cell where you want the SUM() function to reside, press Autosum for SUM(), or the down arrow to choose a different function. 2. Excel will enter SUM() in the active cell and highlight a cell or cells that it 'thinks' you might be trying to sum. a. Tag the cell or cells Excel has chosen. b. Tagging anywhere except corners allows you to move it. Tagging corners allows you to change the area being summed. c. The data_array to be summed will be illustrated in the SUM() function as the tagging parameters change. 3. When it shows what you are looking to sum, press Enter.