It has to be plugged into a pc/other tech first
Turn off the device.
• Connect the phone to a computer or another device via USB Press and hold the Volume Up key and the Power key.
• When the Android logo appears, release all keys.
• Use the Volume Down button to highlight Wipe cache partition.
• Press the Power button to select Wipe cache partition. • Use Volume Down to highlight Yes.
• Press the Power button to confirm the action.