Using a check. Every check below is asked by the Check action, which sends one event when the answer is yes and another when it is no, once or every frame. It is the one action that is not listed on its own.
Already made, and yours to change. A hero is a whole player. A thing is something for the player to meet. A node puts something on the screen, or gives a character something it did not have. Each works the moment it is added, and each opens up to show how it was built.
Each recipe is a small scene that shows one idea. Open it, press Run Current Scene, try it, then click its Machine to see how it is built.
The manual walks you from your first machine to whole games. Here are its contents. Read the whole manual as a PDF.