First method:

Firstly hold down the Power button, until your device is turned on.

Then from the home screen open Menu and choose Settings.

Select Backup & Reset and tap Factory data reset.

Choose Reset device and select Erase everything to begin hard reset operation.

Well done! Your  tablet should restart itself right now.

......................................................................................................................................................................

Second method:

Start by swtiching off the device by pressing Power button.

Press and hold Volume Up + Power key for a couple of seconds.

You can release held keys when you see an Android Logo on the screen.

To enter the Recovery Mode hold down the Power button for a short while.

Afterwards from the menu choose "Wipe Data/Factory Reset" by using Volume buttons to scroll and Power button to select options.

Tap "yes" to confirm if you are 100% sure you want to clear all your data.

Press Power button to enter option "reboot system now".

Cogratulations! The hard reset has just been performed.