Gabriela,
Tom, gave you the basic concept how to do it and nkg2 suggested things to consider.
Here is another basic steps:
Components > Controls
Create couple of controls to turn pump on and pump off at certain time.
If Clock Time >= 2 PM AND Clock Time <= 8 PM Pump-1 status Off
If Clock Time >8 PM and Clock Time < 2 PM Pump-1 status On
With the above control your pump -1 will stay Off from 2 to 8 PM and turn back on outside the interval.
This link will help you understand/crate the controls in the model
http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/creating-controls-conditions-actions-and-control-sets-tn.aspx
Note: Above steps are just off the top of my head