Twists happen at the scene level, events within a scene. In other words, when you start a new scene you check for a twist based on the current stability factor. Once you are in the scene only events will happen, and those are geared toward shading/pushing the yes/no dice rolls. The only guidance for twists is in the "Concepts" section. It is a minimalist process for sure, relying a lot on users to make it their own. That being said, I think it's fairly clear. "add, remove, or alter one of the key elements: character, time, tone, events in motion, etc. You might even try a flashback..."
Say you want a scene where your hero is negotiating with the orc chieftain of the bloodclaw tribe. You roll a twist. Here are some things you might do:
Character - add a wily shaman who will counsel the chieftain however you want him to -- but there is a cost
Time - this negotiation happened before the events of the "now" so you already know it goes south. You are playing the scene to see how.
Tone - you had something super serious in mind. Turns out the orcs are a wild bunch and you must party with them as their guest. How you handle yourself may have an influence on your morning-after discussion with the chieftain.
Events in Motion - the orcs have developed a super weapon you knew nothing about, the negotiation is about the terms of your surrender only, there is no chance they will accept peace thinking they have superiority. Your goal for the scene may be just to try and find out something about the weapon.