The video shows how to make the dialogue appear in game, it’s just two nodes. But what you want to anchor it to, that’s up to you. If you want to click on an NPC to start the dialogue, you have to write the logic behind clicking on an NPC, which isn’t too complicated even for beginners, but it’s got nothing to do with the dialogue itself, we’re already in your game’s logic here.
If you bought the plugin and are having difficulties with that, tell me what type of game you have and what kind of “anchor” you’d like to have to start a dialogue, I’ll see if I can make a few screenshots of how you’re supposed to set it up.