There are 3 easy ways to import the demo data in Gutentor.
Firstly, when you are adding/editing page or post, you will find Template Library in a blue button at the left corner.
Click on it, you will find 3 option for importing the demo data.
In this option, you can import the ready-made blocks in your page or posts. For example About us, Accordion, Author Profile, Blog, Call to Action, Countdown, Counter ,Featured Block, Gallery, Icon Box, Image Box, Image Slider, Opening Hour, Pricing, Progress Bar, Social Team, Testimonial, Video Popup, Timeline, Tabs etc.
In this option, you can import the pre-built template stored in the admin panel.
In this option, you can import the demo blocks from the external source. You will need to import the blocks from the JSON file. You can import from your exported Template Block File