1. Turn off the smartphone.
2. Press'n'hold the Volume Down button for three seconds. As you hold it, press'n'release Power button.
3. Select Recovery - to do that, use Volume buttons to navigate the menu and Power button to select.
4. Android logo will pop on-screen eventually. When it does, press'n'hold Volume Up.
5. Keep holding Volume Up! Press and let go of the Power button.
6. You now should be in Recovery Mode. Shiny. Here, use Volume buttons to scroll through the options and Power button to select them.