Duane's answer is perfect if you just want to change one print out on a
report.
But if you live in a country that uses the dd/mm/yy format, you will want
this changed for all your programs. Open the Windows Control Panel. Go to
Regional Settings. Set your date format there. Access will use the setting
you choose there.
There are still a few gotchas for people who have non-US dates. See:
International Date Formats in Access
at: http://allenbrowne.com/ser-36.html