Information Technology Infrastructure library :- wanted to know about it?

I wanted to do ITIL ( Information Technology Infrastructure library) .

I searched over about this on internet but not able to get the full details and not event he guidance where to start from

I want to know where from I can do this course and where to apply for the same.

And from what level I have to start this course from the foundation or something else...

If anyone know about it please do let me know asap..

Thanks !

Nupur