How to: 9-24V Solenoid w/ PWM on Arduino Safetly

I got this solenoid the other day from a friend. http://www.adafruit.com/products/412?gclid=Cj0KEQjw6J2eBRCpqaW0857k9p4BEiQAWarYbC_9L2mTEY5_PGQuZKPvl3AhG6jmCpmh1cJVYcNBPooaAi9_8P8HAQ

I am still new to Arduinos,I know the Arduino can safly pull 20mA w/o damaing itself. If the coil of this solenoid has 100ohms then by ohm's law 24V/100ohms=2.4A (I think im right), if so whats a safe way to be able to generate this much current and voltage and still be able to use the arduino to control when to turn it on and off. Ive created a block diagram of the program needed for analog input(10bit resolution) to a analog output(PWM 8bit resolution) for similar projects,but never for something this strong.Any help would be great.

This is your link: http://www.adafruit.com/products/412 Click on that page on: "...check this diagram for how to wire it to an Arduino..."

I am sorry, Im not the best at english, even for these posts I had to have a friend check my grammer.Thank you lol

You will need a circuit with a transistor or relay to turn on the current to the solenoid coil.