Doing so places your cursor in the cell. Type =STDEV( ) into the cell. You can press the left arrow key once to do this, or you can click in between the two parentheses in the text box at the top of the document. You can input a range of data cells by typing the name of the first cell in the list of data, typing a colon, and typing in the last cell name in the column. For example, if your list of numbers goes from cell A1 through cell A11, you would type in A1:A11 in between the parentheses.  Your completed formula should look something like this: =STDEV(A1:A11)  If you want to calculate the standard deviation of a few numbers (not a whole range), you can type each number's cell name between the parentheses and separate the names with commas. For example, to find the standard deviation of A1, A3, and A10, you would type in =STDEV(A1,A3,A10). Doing so will run your formula, causing the standard deviation value for your selected values to display in your currently selected cell.

Summary:
Click an empty cell. Enter the "standard deviation" formula. Place your cursor in between the parentheses. Add your data range. Press ↵ Enter.