With the absence of CPanel, managing your website on Google Cloud Platform is a bit tricky. Nevertheless, you’ll find that an FTP or SFTP connection to your web server will come in handy especially when you have plugins and PHP functions that break your WordPress website.
Here is the tutorial I followed and that worked for my case in connecting Filezilla on my desktop PC to my Google Cloud Platform web/file server:
Once you’re connected, you can find your WordPress installation in:
/opt/bitnami/apps/wordpress/htdocs. This location is valid if you installed WordPress via the WordPress Certified by Bitnami and Automattic software from the GCP Marketplace.
Filezilla and Putty Key Generator are safe applications if you downloaded them from valid websites.