In order to hard reset a Nokia Lumia 510, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia Lumia 510 device will be brought back to the default configuration of a brand new device.
1. Turn on the phone.
2. Press'n'hold the Volume Up + Camera + Power buttons. Let go of the Power button when the device vibrates.
3. Phone will now reset and restart. Well done.