You can create menu link for Phoca Guestbook here: Menu » Main Menu (e.g.). You are in Menu Item Manager. Click on [New] button. You are in Menu Item. Select Phoca Guestbook from Select Menu Item Type. Then select Phoca Guestbook in this selection. Add Title. You can change the component settings in Parameters (Component).

Don't forget to select guestbook in Parameters (Basic). If no guestbook will be set, no guestbook will be displayed in frontend.