The Presta valve, is a valve commonly found in high pressure road style and some MTB bicycle inner tubes. You'll find an outer valve stem and an inner valve body on one of these valves. A lock nut to secure the stem at the wheel rim and a valve cap may also be present.
To inflate your tire, first check the PSI you need (found on the sidewall of your tire). Next, If the Presta valve hasn’t been opened for a while, tap on it to release a short hiss of air to make sure it’s not stuck. This same process (hold the valve down longer) will deflate the tire.
This valve is locked with a tiny acorn nut, unscrew it before you inflate the tire and press the stem down to release air. Connect the pump according to your pump's instructions. Pump to proper PSI.
***PRO TIP*** If you’re not sure exactly how hard you want your tires to be, inflate to the max recommended. If – when riding – you feel the road is shaking you about and bouncing you off the ground, it’s much easier to let a little air out than to pump more in. ALSO, note that lots of modern pumps can be converted between Presta and Schrader valves, by dismantling the connection and reversing the direction of parts. Again, check your pump's instruction manual for more info.