rogertee:
the batteries you speak of are lithium ion you can buy battery holders for these but one battery is 3.7 volts fully charged so you should use 3 in series to get enough voltage for the arduino on board voltage regulator.
Please get your facts straight.
LiIon/Polymer chemistry is 4.2V fully charged. The 3.6/3.7V is the nominal voltage.
// Per.