Shut off valves to an area of frozen pipes if just a part of a home is frozen.
If the whole house is frozen, turn off the main valve for the house. If the pipes have burst in the pipe section before the shutoff valve, have the service shut off at the street. The goal is to avoid water leaking into the home from pipes when they begin to thaw.
Open all of the valves to drain down water as the pipes thaw. Even if the traps and fixtures are frozen, adding RV antifreeze may reduce the damage to fixtures. If you do not have antifreeze, add salt to try to reduce the amount of freeze damage. The salt will not know it is in a commode as opposed to on your sidewalk and will melt the ice.