How to become a helicopter pilot?
If you really want to become a helo pilot, just begin a search for a flight school which does helicopter training.  I do recommend Precision Helicopters out in McMinville, OR, but there are plenty of good schools, all with fine instructors, out there.

As with any kind of flight training, it requires three things:

Commitment:  Once you start your training, be prepared to commit to finishing it.  Flying will teach you a lot about your capabilities and limitations as a human being.  Some areas are going to come easily to you, others you are going to struggle with.  But you can persevere if you work hard at it.  It is imperative for success here that once you start, you do not terminate your training or have extended delays or absences from your flying.  Flying aircraft is a perishable skill and lessons learned can erode away if not regularly practiced.

Time:  be prepared to budget at least three months, maybe more depending on how easily you progress, to flight training.  This will encompass 2-3 flights a week with classroom prep on the side.  This is an ideal amount of time as it keeps your flying regular to maintain proficiency in skills learned while allowing you to fully digest and ruminate on previous lessons.  It also gives extra time should you encounter learning plateaus or other difficulties in your training.

Money:  Unfortunately, no bucks, no Buck Rogers.  Flying is expensive and that goes doubly so for helicopters.  For a private pilot certificate with a helicopter class, I would anticipate spending an estimated \$20,000-\$25,000 on your training.  That will encompass all of your costs, including dual flight time, supplies, ground school, simulator work, FAA written exams and the practical exam (checkride) in the helicopter.

The military is another good option for flight training.  However most service branches require that you having been commissioned as an officer before your 29th birthday in order to be eligible for their flight training programs.  You will also need good eyesight and be in excellent physical condition.