It will recharge on it's own once the adapter is plugged in.
Usually, for a laptop, there are LED lights to indicate what things
is for what. For mine, there are 3 LED lights, one indicating
whether the laptop is on, one for battery, the other one for
wireless/bluetooth. Look for the one that indicates the battery (a
battery symbol). If it is charging, the LED light is blinking. Once
it's fully charged, the LED light will not blink anymore.
If the LED light is not blinking anymore, yet your laptop keeps
prompting you to recharge, the battery is faulty. Bring back to
Acer service centre.