Below you will find the necessary steps to achieve that:
Important: When you reset the database, you will lose all the customization and options you have set.
Install WordPress database reset plugin.
Go to WordPress admin menu-Plugins-Add new, and in the right section of the screen look for the WordPress database reset plugin. Click on the Install now button to download and install that plugin.
Activate the Plugin
Click on the Activate plugin link after the download and installation process has finished.
Reset the Database
Go to Wordpress admin menu - tools - database reset and reset the database.