Regular blog posts can be managed in WP Admin → Posts. If you are new to WordPress check out the official documentation on writing posts at https://codex.wordpress.org/Writing_Posts.
It's all regular WordPress usage, check the section below for ViralPress posts.
The theme uses the plugin ViralPress for the non-standard posts ( polls, quizes... ). To create a post click on the CREATE POST button in the top right corner of the header.
For more information on ViralPress check out their official documentation