The plugin is only responsible for displaying dialogues. Interacting with objects (which is what you want to do here) is not part of the plugin, but part of basic Unreal functionality.
The demo projects show a lot of the functionality that people ask about. So feel free to open a normal demo and see how the dialogue opens there, then re-implement the same thing in your project.
To give you an idea, let’s assume you have an NPC class. It should have a field of type Dialogue. You put your dialogue asset in there. If you want to talk to that NPC, do a raycast from your camera a few meters forward and if you meet an NPC, open a dialogue using his dialogue asset. This is basic unreal, there’s no plugins for this.