Overclock Rspberry Pi with raspi-config

To overclock your Raspberry Pi, enter the command:
$ sudo raspi-config

In the steps, use key to select options, to switch between options, and various actions. And to confirm.

- Select Overclock and press

Be aware that overclocking may reduce the lifetime of your Raspberry Pi. If overclocking at a certain level causes system instability, try a more modest overclock. Hold down shift during boot to temporarily disable overclock. 
See http://elinux.org/RPi_Overclocking for more information.

- Press to confirm.

- Reboot.