First you have to create a timeline Layout which contain settings of timeline post layout.
1. Go to ‘WP Timeline PRO’ in admin menu.
2. Click on ‘Create New Layout’ button.
3. Select Timeline Layout Template and give name to layout.
4. Select ‘Post Type’ to show posts in timeline
5. Select ‘Page’ to show timeline.
6. You have many other option to customize timeline which describe in detail documents
7. Finally click on the save button.