According to the manual the charge lamp is on the back of the camera near the upper right corner of the LDC screen (see page 3 of the manual).
Green and blinking slowly means the battery is charging.
Green and blinking quickly means any one of the following:
The ambient temperature is not suited to charging. Charge
the battery indoors with an ambient temperature of 5°C to
35°C (41°F to 95°F).
• The USB cable is not connected correctly, or the battery is
faulty. Make sure the USB cable is connected correctly and
replace the battery if necessary.
• The computer is in sleep mode and is not supplying power.
Wake up the computer.
• The battery cannot be charged because the computer cannot
supply power to the camera, due to the computer’s settings or
its specifications.
Nikon Coolpix P510 manual