How to add an instance of a class into an array of another class (Ruby)

I have two files in my directory, one which is garage.rb & another called car.rb.

car.rb file just holds a car object:

class Car
end

garage.rb file is as follows:

require 'car.rb' #Makes car class accessible in garage.rb

class Garage
  def initialize
    @capacity = []
  end

  attr_accessor :capacity

end

When I make a new instance of a car by calling car = Car.new, how do I put car object in the @capacity array my default?

Essentially, whenever I call car = Car.new, I want car to be put in the @capacity array instantly.

I understand that I could make a function like so:

def add_car_to_garage(car)
  capacity << car
end

But, I want the car to start in the garage when it is created, so I don't want a method to add it to the array, I just want it to automatically start there when the instance of car is created.

Any advice would be appreciated. Thank you.