I love that I can use this to charge my iPad or my Android. Pretty easy to use - Just use the hole marked "5V in" to charge up the device, and use the "5V Out" slot to charge your cell phone. Common sense really, considering there's only one end of the cord that you can plug into your phone...the other end obviously goes into the portable charger. The light on the device turns from red to blue when it's fully charged, and you will need to press the button when charging your cell phone so that the blue light is on. To give you an idea of the charge time/amount, I drained the battery on my Nexus 5 down to 14% and it took this charger just under 3 hours to bring it up to 74% before it died. The charger was fully charged and I didn't use my phone while charging. So you probably won't get a full charge from this, but it'll at least give you some extra time.
I ordered a number of these for Christmas gifts, specifically because I wanted a higher capacity item. The description said it was 32,800 mAh for 2, and the product Q&A confirmed this -- clarifying it was 16,400 mAh each. When the items arrived, it states on the label they are 2,600 mAh each. I was mislead, and there is no time to return them and find a substitute.
I ordered these as Christmas gifts so I haven't actually got to see how long they will hold a charge or anything of that nature but willupdate when I have some more info. However these ARE NOT 32800 mAh batteries. THEYARE 2600 mAh batteries. Which explains the great price they are being sold for. I did charge them and tested them and they seem quite nice. The case is aluminum and a nice size so hopefully they can fully charge a phone. If they in fact are god at charging things I will rate them as excellent.