Hi everyone,
      I am in the build phase of my first DIY quadcopter. I bought a Spektrum DX6i as it has a good rating and is about as expensive as I can go right now. I was reading the instruction manual and there is nothing in there about multirotors, only Airplanes and Helicopters. From what I have read I thought that the RC transmitter was common to all three types of aircraft. If so how do I configure a quadcopter on it. Do I just use the default settings?

For Multirotors use the Aircraft option, never a Helicopter.

You probably know this, but just in case....
When you go to set up controls, Throttle is throttle, Aileron is roll, Elevator is pitch, Rudder is yaw.

There are some videos on YouTube search for "spektrum dx6"

I use the same transmitter. I put it in airplane mode and that's it, expo and rates are set through the flight controller.