How do I answer the doorbell remotely

I have just installed a second generation doorbell, and downloaded Ring app on a Android phone. I assume everything is working ok as I get an alert when there is movement Infront of the bell or when someone presses it. What I don't know is how to answer the bell when I'm not in. It seems ridiculously basic but I can't find anything in the manual that tells me how to use it. When I get the bell alert, I can swipe down and after a few seconds I see a small video of what the bell camera sees and below it are three icons a red phone, a microphone crossed through, a speaker crossed through. So how do I have a conversation with the caller?