Adding an additional light fixture and powering it from an existing gang box is not complicated if you expand the existing gang box and power both lights with separate switches. Some gang boxes are in locations that do not allow the box to be expanded to add a separate light switch. You can wire two single pole light switches in the same gang box using a device that combines two separate single pole light switches into one device, using the original single switch space.
Things You'll Need
Red wire connectors
Combination two single pole light switch device
Phillips or slotted screwdriver
Outlet cover plate
Turn off the breaker inside the main breaker panel that supplies electricity to the light switch gang box.
Connect the three white wires inside the gang box together by twisting a red wire connector on all three wires. Connect the three bare copper wires together with another red wire connector. Push these two sets of wires into the back of the gang box.
Find the two copper screws on the combination two single pole light switch device that connect together with the copper metal tab. Wrap the black power supply wire around one of the copper screws. The power supply wire connects back to the main breaker panel.
Wrap the black wire from the original light fixture to the copper screw on the opposite side of the combination device. Wrap the black wire from the additional light fixture to the remaining screw on the opposite side of the device.
Tighten all three screws to hold the wires to the combination two single pole light switch device. Push the device and the wires inside the gang box and attach it at the top and the bottom of the box with the screws provided with the device. Cover the two single pole light switch device with an outlet cover plate.
Turn on the breaker inside the main breaker panel that supplies electricity to the light switch gang box.
Test to verify that you have disconnected the electricity in the area you are working to avoid electrical shock.