I will ask this.
How can I build this ESC, and what is it do?
Is it like a normal PWM generator?
The motor has 3 wires, red,black and yellow.
Why cant I just plug the red and black to +5v?
If you put RC ESC into google you get roughly 2230000 results...
You need an ESC.
You will not have the knowledge required to make one.
You need to buy one.
You need to buy one that provides enough current for the motors you have (20A).
You can then control it via pulses (using the servo library).
Please go and look all this up. You will find all the info you require.