There are 2 ways to insert a quiz.
1) Using Gutenberg block
The easiest way is probably Gutenberg. Just find the block "WP Viral Quiz", select a quiz, and save. Done!
2) Using the short code
If you like to use shortcodes, you can also use this method to insert the quiz somewhere on your WP.
Just look at the [shortcode] column in the quiz builder. Copy and paste this shortcode to the content of your page/post, and save it ! The quiz will appear on the page.