How to drain fresh water tank?

The Styrofoam-insulated tank looks like your hot water tank with the three valves set for normal use.  I can't tell what the picture with four water pipes with valves is, I don't have something like that in my camper. 

My low point drains do not have a valve on them, just a screw-in cap.  they just drain the plumbing lines as open spaces describes. They are located on the outside underneath the camper.  My freshwater tank also has its own drain hose with screw-in cap (no valve) located outside underneath the camper.