There is more to changing a tire than it seems. If you just tried doing it raw without any instructions or experienced help, then don't be too disappointed in the results.
Go to your local library and get a book or video on bicycle maintanance. There should be a section on changing bicycle tires.
The other option is to go to your local bike shop or bicycle club, or friend who knows how to change a tire and ask them to teach you how to do it.
There are fine points too numerous to mention on a hand-typed bicycle forum. It is a good skill to learn, so learn from the best teachers you can find.