Click the cell where you want the result
Type `=A1-B1`
Replace `A1` and `B1` with the cells you want to subtract
Press Enter
To subtract more cells, use `=A1-B1-C1`
To subtract a number directly, use `=A1-5`
To subtract across rows or columns, drag the fill handle after entering the formula
To subtract a range from a value, use `=A1-SUM(B1:B5)`