Amy - real easy - pick your starting point - (the grade that you want to make everything else level to), this is where you put the bucket, measure from the ground up to the water level in the bucket - write this number down (reference num).
Take a stake and pound it into the ground at the next point you want to check your elevation at, tape the tube to it, there will be a water line in the tube, measure from the ground up to the water line, this measurement will be either:
1. less than reference num - you have to remove dirt until equal to reference num
2. More than reference num - you have to add and compact dirt until equal to reference num.
3. Equal to reference num - you have to do nothing

Move onto next spot - using same stake or new stake - repeat until everything is checked