The SUMIF statement in Excel allows you to quickly sum values that meet specific criteria. To use it, you first need a table of data with at least one column of numbers. Then, create a new table with a criteria column and a result column. In the cell where you want the sum, use the SUMIF function by selecting the range of criteria cells, the criteria to match, and the range of cells to sum. You can copy the formula to other cells, changing only the criteria to automatically calculate sums that meet different conditions.