The rtc4000 is very easy to use, simply connect the tyre inflator to your tyres or other application, press and hold the blue power button in the centre of the inflator for 3-5 seconds the led screen will illuminate you can now set the pressure by pressing the plus button which will increase pressure or by pressing the minus button which will decrease pressure, then press the blue button which will start the tyre inflator, once the device reaches the desired pressure it will automatically cut-off. You can also use the 4 preset memory settings which store your desired pressures, to do this press the button with a circle which will take you to memory 1 (M1) you will need to set psi or bar or kPa press and hold the circle you will see the device change from psi to bar or kPa, to set the pressure press the plus button once you have the correct pressure, the pressure will stop flashing which means the pressure is now stored under M1, you can do the same for the other 3 memory settings.