This will depend on your privacy settings. If you have enable Wedding Code or Guest List Match, guests will either have to provide your wedding code or their names & email, or both. If you've left your site public, then anyone can write you a note.
Guestbook:
- If private: Guests log in to the Appy Couple app or wedding website with the wedding code, or name and email address
- Tap “Guestbook” on the site navigation or click on the notebook icon on the app
- Start typing directly into the text box
- Click the camera icon to add a photo
- Tap “Post” to submit your message.