Check the tyre sidewall for the recommended tyre pressure (psi or bar)
Use a tyre pressure gauge (digital or dial)
Make sure tyres are cold (check before driving or after the car has been parked for a few hours)
Remove the valve cap from the tyre
Press the gauge firmly onto the valve stem until the reading stabilizes
Note the reading
Compare the reading to the recommended pressure
If low, add air from an air pump and recheck
If high, release air in short bursts and recheck
Repeat for all tyres, including the spare if it’s meant for use
Replace the valve caps securely
Recheck pressure after adjusting, and again after driving a short distance if needed