I bought a portable battery charger. Now what do I do?

So I went to my local Wal-Mart and I was looking for portable chargers, and I was looking for one of the chargers similar to what my work uses for our headsets/scanners/work phones. The cylinder ones, very much like the one linked here: http://bit.ly/2ikhIwO.

But that was not the case. I bought a BlackWeb 5200 mAh charger (only $15). Comes with USB port charges a smartphone or tablet. Works with USB-charged devices including iPhone, iPad, Samsung and other Android-based smartphones and tablets. Includes Micro USB charging cable. Up to 2X extra charges.
(Not my eBay page, but this is the item here): http://ebay.to/2inGqyA

All that said now, one feature is the LED lights that indicate the devices battery life. I assume it is rechargeable anyway, if it is not a one-time only use.

My question though, are these things rechargeable by just plugging them into the wall like I would my cell phone?

If anyone has further information on if chargers like these, please let me know. New to this whole thing.

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