If you want to delete a database, it is recommended to download a backup of your database beforehand, as this is a non-reversible action.
Once you're ready to delete the database, navigate to Websites → Manage, search for Databases Management on the sidebar and click on it:
Find the section List of Current MySQL Databases And Users, click on the options button (⋮) next to the desired database and select Delete:
On the pop-up window, click on Confirm Delete. That's it, your database and its content is permanently removed from your hosting plan.
If you prefer to keep the database structure and only empty its content, refer to this guide: How to Delete All Database Tables 💡