The first step is to book a trial lesson with your local flying school.  This is usually a 30-60 minute lesson with an instructor, and you'll usually get to have a go at flying the plane under instruction.  After that, there's a number of routes to your license that the school will go through with you.  For me, I had to do a minimum of 45 hours flying instruction, as well as several 'milestone' flights (first solo, qualifying cross country, skills test).  There's also a series of written exams to do.  Once you pass your skills test, you get your license and are free to go flying!