Click the cell where you want the total to appear
Type `=SUM(`
Select the range of cells you want to add
Type `)`
Press Enter
Use AutoSum by selecting the total cell and clicking `AutoSum` on the Home tab
For a column total, select the cell below the numbers and press `Alt` + `=`
For a row total, select the cell to the right of the numbers and press `Alt` + `=`
To total non-adjacent cells, type `=SUM(`, then select each cell or range separated by commas, then `)`
To total an entire column, use `=SUM(A:A)`
To total an entire row, use `=SUM(1:1)`