If you leave either name box empty, it will match all entries. Note
that you can put in part of a name and it will return all names that match that
portion. If you leave the unit selection at Select Unit... or All Units,
it will return people from any unit. If you leave the year selection at Select
Year... or All Years, it will return people from any year.
Note that many people do not have units/years listed, so if you cannot find the
person you are looking for in a particular unit or year, just try the search
with name alone. To find the people in a particular state, try leaving all other
fields blank.
Finally, always remember that computers do exactly as they are instructed, so the less information you enter, the better your chances of getting a hit.