Can I add pedal assist to an e-bike?

It looks like that kit doesn't mention anything about Pedal Assist. There is usually an extra 3-pin connector on the black control box, if you can't see anything it could be inside the box. You should probably email Aotema and ask them. Failing that you can always get a different controller with pedal assist and then wire the new controller yourself. Make sure the motor is the right specifications for the new controller.