you need a wrench the right size for the nuts that hold the wheel on your bike .
old schwinns may not be metric though metric axle nuts tend to be 14 or 15 mm

maybe you would feel better asking your father , how big a wrench you need ..

though you would not be to surprised how bike shop guys fall all over them selves
to help a young college age woman that comes into a bike shop, asking the most basic questions..

..Isn't there a Co Op bike shop as part of the student union outdoor recreation services,
at your university ?, ask there , bring the bike.