To edit a step in your Automated Workflow, you need to select the group and then select the Automated Workflow sub-tab.
From there, click on the message title in blue that you want to edit.
Once you're in the actual message, you can change the content, message type, message body, or the scheduling of when it gets sent out. Simply click on the section and make the desired changes.
Click Save Step at top when finished. If your message shows a red dot next to it, it is inactive and will not send. To make active and sending, click "Activate Step" when editing the details of the message.