If you have a particular message related to the agenda to share with the participants, please add it by accessing Configuration - Content Snippets and by clicking on Change Content.
Your message will be displayed on the event Agenda on the website.
The text will be also displayed in the participants' agenda, both on the website and in the PDF agenda. You can change it at any given time.
If you want to add a message displayed throughout registration, you can do it via the Registration Snippet.
The message will be displayed at the top of the page, in every step of the registration. You can change it at any given time.