Method 1:
1. Hold Power Key To Turn Off Your Smart Phone.
2. Press And Hold Volume + Power Key Turn On Your Device.
3. when android Logo appear on the screen Release all keys.
4. Now use Volume down key to Select this option "Factory reset" Power Key To Confirm. wait few second.
Done.
Method 2 :
Make Sure Your Device is Turn On.

Now Go To - Home / Main Menu :::
Than Select - Settings Tap Backup And Reset
Now Chose Reset Phone Select This Erase all data.
Select Ok Confirm
Done