[PicoCMS] How to access the content files

Hi all

A question, how to manage the files of this FlatFileCMS:

My YunoHost server

Hardware: HP Proliant MiniServer
YunoHost version: 11.0.9
I have access to my server : all
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no

Description of my issue

Installation of PicoCMS works fine. But how did you manage the files, extensions, themes?
I connect via STFP with the admin account to the YunoHost. I see the structure of the linux file system: I found also under var/www/pico the (probably) the folder for manage the files. But with the admin account I receive under the folder var/www/pico a “no access” message.

btw: I use sftp because I want later copy the md files from a other application to PicoCMS.

Anybody can help?
Daniel