If you are new to Amazon AWS Lightsail, You might confused to find the default htdocs location of your website because it is bit deferent than other Linux systems.
So, How to find the root directory on Bitnami (WordPress) on Amazon LightSail?
Navigate using your FTP client as follows,
/opt/bitnami/apps/wordpress/htdocs/
or
/opt/bitnami/wordpress/wp-content
By default all user files are uploaded to /opt/bitnami/wordpress/wp-content