Smart Reply suggests quick responses in real-time during a conversation. Once active, you will see the suggested replies in the conversation area, if any. There are two ways to populate the suggestions: via bot, via agent Assist.
Bot Suggestions
To use the bot’s suggestions just sync Dialogflow normally and train the chatbot as usual. The same chatbot used for the users will be used.
Agent Assist Suggestions
Agent Assist requires technical knowledge in order to work and it’s intended only for enterprise business with a data set of at least 30.000 conversations. If you never used Agent Assist you most likely don’t have the knowledge and data to use it, and so you can ignore it. More details at https://cloud.google.com/agent-assist/docs/conversation-profile.
Information
Smart reply first look for a suggestion from the bot, if there is at least one it returns the results, otherwise look for the suggestion via the agent assistant if available. The agent assistant is never used if the chatbot gives at least one hint.