The manufacturers offer their way to factory reset the phone. You can check the whole procedure on the following link: http://www.bluproducts.com/r1-hd-device/r1-hd-factory-reset.html
For hard reset, use the following instructions, but be careful as you'll wipe all the phone's contents:
Make sure the battery is charged to avoid any errors.
- Turn off your phone.
- Press and hold the Volume Down + Menu Button + Power Button.
- Wait on the phone screen for the menu to appear.
- Select option "Wipe data/factory reset" using Volume buttons to scroll, and Power button to confirm.
- Choose from the menu "Yes -- delete all user data".
- Then press Power button to enter "reboot system now".
It will take a while before the phone will be usable again.