It didn't seem to be pre-charged, so I plugged it in to a wall outlet until all 4 lights were lit.
It wasn't difficult to learn which way to use it to charge my phone device. I had 2 test-runs.
First I had a trip an hour in each direction. On the way there, I used a lead I already had linking my phone to the car cigarette-lighter port. Here my phone lost 5%. On the way home, I linked my phone to the power pack, and the phone gained 10%.
My second trial was a 2 1/2 hour trip. Here I relied heavily on the phone GPA. Using the car-to-phone lead, my phone lost about 25%. On the way home, using the power pack, my phone went back up to 100%, and also recharged a passenger's phone which was below 50%.
Now I feel quite confident using this power pack for an upcoming 4 1/2 hour trip. Before coming back home, I'll be able to recharge the power pack in one of the outlets in the motel room.
Asked if I would recommend to a friend - yes, I already did!