Copy the Assets folder to somewhere inside your projects Assets folder. You may rename the folder to whatever you'd like. The Examples folder is optional. It also requires Text Mesh Pro
Dialogue Flow is a tool to create quick dialogues in Unity 2018 (untested in older versions)
This is just something I created just to have something I made with Unity. I wouldn't really recommend using this as is. I would recommend building off this and probably changing the DialogueNode.eventMsg to a struct with like an enum + some value. That way you could create 1 single DialogueEmitter with some sort of switch statement in the OnFlowEvent method so you wouldn't need to create a different emitter for each dialogue flow that has an event.
For more information read here.