The first action to do, is to create a guestbook. Without a guestbook your visitors cannot add messages into your guestbook:

Components » Phoca Guestbook » Guestbooks » [New] button. Now you are in Phoca Guestbook - Guestbooks [New]. You must fill the 'Title' field. You can add some additional information into the guestbook. This information will be displayed in 'Guestbook view' in the top of the content. Click on save and your guestbook will be created. In the list of guestbooks, you can publish, unpublish, edit, delete, move the guestbooks.