1. Create the numbers in the cells that you wish to sum the span of. To sum the span of cells, you will first need to create a series of numbers that you wish to be summed. You can create lists vertically or horizontally depending on your preference.
2. Select the cells that you wish to sum by highlighting them. To highlight the cells that you wish to sum the span of, simply left-click on the first cell and hold the mouse button in as you drag the cursor over the other cells that you wish to sum. Release the mouse button once you have highlighted the desired cells, and they will stay highlighted.
3. Use the 'sum' icon on the command bar to easily implement the formula. The sum icon is located on the top of the command bar in the middle and looks like an 'M' lying on its side. A drop-down menu will open when you click on the sum icon. Select “sum” to create the formula.
4. Save changes to your spreadsheet. You will want to make sure that you save the changes you just made by clicking on the “file” tab and selecting “save.”