How to control Arduino robot wirelessly?
A 13 year old programming an embedded device? Good luck to you, if you conquer it you will be years ahead of your age group. 

What you need to understand are the fundamentals; how can you transmit a 'pot' over an XBee? That is an electronics question, start there. You will find that another arduino or laptop is probably required. The XBee itself requires some sort of host adapter, and it might as well be another Arduino since something has to electronically read the 'pots'.

Then you need to develop your own protocol for signals sent between the 2 Arduino (over XBee or on a serial wire , it is the same).  There are many already out there, but they assume you know the basics before you use them (eg firmata). This is the basics.

The fact that your google results showed nothing similar is probably a good indication it can not be done as you had hoped.

update: I like @gerben comment, but even as an advanced person, I would find it challenging.