You’ll delete the files by accessing your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these).
And, you’ll typically delete the databases in your hosting account’s control panel, either a “Databases,” “MySQL,” or “phpMyAdmin” section.
All of this varies greatly depending on the hosting provider, so please consult your hosting provider’s documentation for specifics.
