So I'm making a game where, when you make a certain action, one of two things will happen. I don't understand how to actually make it where two possible things could happen with set chances. I would want it to be a one in six chance of one thing happening, and a five in six chance of something else happening, all after a single action. How would this sort of thing be implemented in the design process?

Scripting-wise, you can do something like:

if (GetRandomInt(1,6) = 1) {
// do the 1/6 thing
} else {
// do the 5/6 thing
}