How can i use the button reply in a whatsapp flow?


I used interactive buttons in a whatsapp flow, but i can’t find the button anywhere.
I just added a send a message and in there I added a signup button. Now once clicked i want a google sheet field to change to Registered. But i have no Idea where to fetch that data and how to trigger the add row.

Only thing I saw in here is that it should be under messages - button reply but i don’t see that anywhere…