You generally do not need to do opposed rolls in this system, but there's some times where it may make sense. Perhaps there are two players who want to decide a contest of skill between each other. The rules for that are fairly simple to follow.

First, instead of an outcome that people can success or fail at, the GM should divide an outcome in half in a way that seems make sense. If it's a binary outcome, 1-3 are one player and 4-6 are the other player, or maybe they want 1 and 6 to be the full successes and everything else is the muddy middle, or maybe 1, 2-3, 4-5, and 6 as four different outcomes. The only important thing is it should be a mirror, with each side getting half the die.

Then, starting with one die for the one outcome, players figure out how many die they would be adding to the roll. Whoever adds the most die is who is making the roll, but they first subtract the die the other player would have added.

I.e., if someone has two dots and the other has one dot, the person with two dots will start with one die for the outcome, add their two dice for their dots, then subtract one for the other player's dot, for a total roll of two, and they can pick either of the die. And obviously, if they're perfectly even in skill, there's only one die, that's the number, so it doesn't matter who rolls it.