Charging li-ion batteries with protection circuit
That board doesn't provide any recharge facilities, so yes you should still use a proper Li-Ion charger with it.

The purpose of that board is to protect the batteries in case of "error".

It will:


Shut off the batteries when their voltage gets too low.
Shut off the batteries if the current draw exceeds 4-6A (short circuit).
Provide an estimation of the charge left in the batteries ("fuel gauge")
Prevent "over-charging" of the batteries (too high a voltage placed across them)


Two of those (over voltage / short circuit) could cause the batteries to explode, the under-voltage can cause the batteries to become useless and unable to be charged.