Once you click on the "edit this post" button, you will see the widget change into an editing menu. To save your editing and go back to viewing mode click on the "Go back to view mode" inidcated by the
blue arrow.
To add new components to your post, drag and drop them from the menu into your post. The components are indicated by the
red arrow. You can also add tags to your post, which allows it to be found easier from the search widget. The
yellow arrow points to where you can add and/or modify tags. The black arrow indicates where the option to move the post into the trash.