How to use potentiometer on one Arduino to control servo on another Arduino via WiFi?
(Yes, I only have links in my answer. And they tend to rot. But in this case it shouldn't be too hard to find those tutorials, nor is the content very specific. I also somewhat feel there should be some help to this person before his question gets closed)

Try to focus on one thing at a time.

Follow the steps below, they should be self explanatory. If you run into trouble, you can always create a question based on that particular problem.

Doing so, you'll learn much more about programming/Arduino as by copying code (and having no idea how to). Sooner or later you'll run into the problem that people will not give you "ready to use code".


Get an Arduino to read out a potentiometer. There are lots of tutorials about that.


https://www.arduino.cc/en/tutorial/potentiometer


Get an Arduino to run a servomotor


https://www.arduino.cc/en/Tutorial/Sweep


Combine these two.


https://www.arduino.cc/en/Tutorial/Knob


Make a wired link between two arduino's


http://robotic-controls.com/learn/arduino/arduino-arduino-serial-communication
https://www.arduino.cc/en/Tutorial/MasterWriter


Make the potentiometer control the servo over the wired connection.
Make a wireless link.
Port the wired link to the wireless communication.