Often a wall receptacle from an upper floor can be used as a source for a new ceiling fixture below, but a switch loop must be run to a wall switch in addition to fishing the cable from the source.
The wattage rating information for a particular device may be on a label or imprinted on the back somewhere. If no wattage rating is displayed, the load can be calculated by multiplying the amps drawn (appliance amps) by the voltage of the circuit. If neither the amps nor the wattage ratings for a device is known, the chart below lists common household appliances and the average watts drawn for each to aid in calculating the load of a circuit.
Reinstall the wallboard strip. Trim along the edges with a sharp drywall knife first to remove any torn paper that could created a gap behind the molding.
Split the sheathing on the cable leaving about 1/4in still covering the wires. Cut the sheathing to remove it and strip off about 3/4 inch of the plastic insulation from the end of each wire. Avoid nicking or scratching the copper wire while removing the insulation.