Like he said, it's not difficult, but you need to know how it works.

Make sure that you're using a pump made for presta valves. Many floor pumps have chucks with two holes in them - one for Schrader, one for Presta. Other pumps have removable/changable parts in the chuck - one configuration for Presta, another for Schrader. Check your pump instructions or post a picture of what you have.

With a new tube in a tire, you have to make sure you can get the pump on the valve stem without pushing it (the stem) into the tire. Put the little knurled nut on the stem, or simply push against it from outside the tire.

You have to open the valve in order for the pump to work with it.

Take a look at the many websites and videos from this search. Hopefully it will make sense to you: http://search.yahoo.com/search;_ylt=...8&fr=yfp-t-600