The Post Timeline plugin allows users to create two types of timelines: 

1. Tag-based
2. Date-based. 

To create a tag-based post, please follow the below steps:

1. Log into your WordPress admin page
2. Click on “Add New” under the “Posts” section

3. Fill in all the required information for the post (content, images, post date, page URL, etc.)
4. In the “Tags” section select an existing tag or create one by clicking on the “+ Add New Tag” 

5. Click on Publish to create the post
6. Repeat steps 2-5 to create additional posts (if needed)

Now that you have created a tag-based post, it’s now time to add it to a timeline. To add the tag-based post to a timeline please follow the below steps

1. Click on “Add New” under either the “Pages” or “Posts” section
2. Click on the “+” icon to add a widget
3. Type “Post Timeline Shortcode” in the search bar

4. Select the “Post Timeline Shortcode” widget, and click on “Add Shortcode”
5. Go to the “Post UI” tab 
6. Under the “Select Tag Type” option select “Tag Based”

7. Select other relevant options, and press “Insert Shortcode”
8. Click on “Publish” when you are done

You have now successfully created a tag-based timeline. Click on the “preview” button to see how your timeline looks.