Presta Valve Instructions...

If you've never used a Presta valve (this article explains the difference) it can be a little puzzling. A schrader valve just inflates, but a Presta valve needs to be opened before you can inflate it.

They say a picture paints a thousand words, so here it is. You need to unscrew the tip first. Just a few turns, and then you should be good to go. Attach your pump and air can now get into the tube.

You'll know it's open as you can press the end gently and air will rush out.

Once you're done, remove the pump head gently. Make sure you screw the valve tip closed, and that should be it.