How to get event action from the button

Development
1

i am using below code to display button in messages, but i need event when user clicks on the button to show another couple of messages of todo responding from api.

can any one help on this

"actions": [
            {
              "type": "button",
              "text": "Todo List",
              "msg_in_chat_window": true,
              "msg": "todo list"
            },
]