Click the cell where you want the total to appear
Type `=SUM(A1:A10)` replacing `A1:A10` with your column range
Press Enter
To sum an entire column, use `=SUM(A:A)`
To sum multiple columns, use `=SUM(A1:C10)`
To use AutoSum, click the total cell and select `SUM` from the toolbar or functions menu
Copy the formula to other cells if needed
Adjust the range if new rows are added