It is very easy to charge an electric bike and you can charge most eBike batteries whilst they are still clipped on to your bike (or you can remove the battery for charging if you prefer).
To charge your eBike simply plug the small charger into a wall socket.
The actual time to charge an electric bicycle battery depends on:
The capacity of the battery. The larger the battery capacity, the longer the charge time.
The power of the charger. Travel chargers and car charges may charge at half the rate of a standard charger. See notes on Ultra Fast chargers below.
How flat the battery is at the start of the charge cycle (batteries last longest when operating between 30 and 80 percent of capacity. Try to avoid fully discharging your battery as this reduces battery life.
The battery technology (lead-acid, Lithium Ion etc).