Not all tire valves are alike. Many people discover this the hard way when they go to inflate their tire and discover that the inflation device doesn't fit the tire valve stem. Cyclists are more likely to discover this, as bicycle tires can feature either Schrader or Presta valves. You can identify Presta valves by their much smaller stem diameter than the more common Schrader style. Presta valves also have a built-in valve stem cap. You can generally find Presta valves on performance-oriented bikes.
Remove the plastic valve stem cap. Even though Presta valves have a built-in valve cap, a removable plastic cap protects the tip of the valve stem.
Read the recommended tire pressure on the sidewall of your tire. The manufacturer typically prints the recommended tire pressure on the right drive-side of the tire, just above the valve stem itself. Don't exceed this recommended pressure.
Unscrew the built-in valve cap at the tip of the valve stem. Screw the Schrader-to-Presta valve adaptor onto the stem. Ensure that it's fully seated. This step assumes that your pump is made for Schrader-style valve use. If the pump head is too large to fit the valve stem without an adaptor, the pump is made for use with Schrader valves.
Fill the tire with air. Remove the pump head, and unscrew the Schrader-to-Presta valve adaptor from the valve stem. Screw and close the built-in valve cap, and replace the removable plastic cap.