Pour the cement mixture into the form you want to fill with concrete. If you are installing a fence for example, you'll want to set the post in the ground and position it correctly, then pour in the concrete powder.
Attach your garden hose to a water supply and run the hose to where the hydrostatic cement is to be used.
Turn on the water to your garden hose all the way so you have a single, concentrated column of water. Direct the water into the form so the action of the water churns up the concrete.
Fill the form with water, and then turn off the water. Allow the water to seep into the concrete by itself. You don't need to mix the concrete with any tools.