How to use a UI Canvas as a UI in Dialogue Manager

Hi, I have recently designed a UI on a canvas, and I have also used dialogue manager to make a conversation, however I am unable to use the very simple UI I have designed as the UI for the conversation because it does not classify as a UI. I probably am either missing something very simple or am doing it completely wrong. Be that as it may, I was hoping someone could give me a few pointers in the right direction. At this point, I have a simple canvas, with three children all of which are buttons, at this point, I just want to be able to use the canvas, and the three buttons as choices for the conversation, with subtitles displayed at the top of the screen.

Thanks, hope to hear from someone soon.