Once you've added a creature, conversations are very easy.
Go to the webpage and create a conversation file for the creature that you want to have text to say.
Add their name or some unique identifier.
Open the creature's properties page and go to the conversation editor.
Edit the conversation using standard toolset conversation rules and then save the conversation file to be the same as the file on the webpage.
As always make sure you're uploading your blueprints when you upload your module.