You don't. Look at sumproduct (link below) if you want to return a numerical
value (sum based on multiple conditions). There is also a link from this
site to Chip Pearson's site that discusses array formulas. If you want to
return text based on multiple conditions, try Index/Match in an array formula.
Alternatively, create a new column and concatenate the columns with the
criteria to create a unique key (like =B1&C1&D1), then use VLOOKUP on this
new column.
Please consider using the conditional sum wizard that will do the summing up
for multiple conditions. You will find this feature in the Tools Menu. If
you are not finding it, choose add-ins in tools menu and activate Conditional
Sum Wizard. The wizard will guide you thro the process of summing a range
against multiple conditions.