[Jared Russell]

What model of encoder are you using?

Most FIRST encoders will have 4 pins (some have a 5th).

One of these should be labelled VCC in the datasheet, and should be connected to the red pin of a digital input port for power.

Another is labelled GROUND and should be connected to the black pin of a digital input port.

The other two are the signals for Channel A and Channel B. Each one should go into the white pin of a digital input (assuming you want to detect direction as well as speed).

If there is a fifth pin, it is most likely for index and you can ignore it.

A motor can go either to a Victor or a Spike. The Spike can only make the motor run full forward, full reverse, or not at all. The Victor lets you vary the speed of the motor as well. Which one you choose depends on the application. Note that big motors (like the CIMs, Fisher Price, or Globe) should go to a Victor with a 30A or 40A fuse - the Spike is fused at 20A, which is well below what the bigger motors can draw.