How do i control a normal electro motor (not a stepper) ?

Well i have a normal 9 volt DC electro motor who i would like to control by an arduino.
I am thinking of putting it on the same 9 volt as the arduino board but not feeding it directly by an arduino pin.

Instead one the pins should control how much of the 9 volt enters the electro-motor.
I have some mosfets which i think would be able to switch 9 volt, from a mosfet shield that works up to 24 volt.
but i am not entirely sure on how to wire this together, since a mosfet does on/off , its not a scaling voltage.

Could someone help me here a bit, i am a beginner into electronics
Programming is fine to me i can do anything there for this, but i have no background into electronics.

If you want the 9V motor to go only one direction with adjustable speed then an NPN transistor or N-channel MOSFET would work. The MOSFET would have to be a logic-level (controlled by 5V) MOSFET to work properly. A Google search will get you more details.

If you want to control direction of rotation as well as speed you will need something called an H-Bridge. Agaib, Google will provide more details.

its not required to reverse its direction, but i need to change its speed.
How is that possible with a mosfet ?.

Since my understanding from mosfets is that are a on/off switch. not something that changes voltage
And from what i know of transistors for them 9volt driving a dc electromotor blows them up (they melt) ??.

Follow this tutorial, except that it is generally a bad idea to power a motor from the Arduino 5V terminal. Use a separate battery pack to power the motor, making sure to connect the Arduino ground and the motor battery ground (negative terminal) together.

You can control speed with PWM, ie analogWrite() to the switching transistor.

You need a reversed diode (eg 1N4004 for motors up to 1A) across the motor to deal with the fact that it is inductive; this is necessary to prevent your transistor from blowing up from the inductive kick off the motor when switching it off (500 times per second with PWM!).