Pull the tank up and out of the unit.
Turn the tank on its side and locate the rubber stopper that closes the tank.
Pull out the stopper. The edge of your fingernail works best but the stopper is pretty easy to dislodge and it shouldn't give you much trouble no matter what method you try.
Dispense vape juice into the tank. The filling port is relatively small but you should be able to fill the tank using either a glass dropper, a needle nose plastic bottle or an e-juice syringe.
Replace the rubber stopper and press it firmly in place.
Snap the tank back into the top of the unit. The tank is shaped so that it's obvious what orientation it needs to be in order to fit in place. Make sure the tank clicks into place and that it is flush with the top of the unit.
Enjoy your new Nautilus Prime e-cig starter kit!