I'm using an excellent web file manager (Sprutio), open source, in my VPS (Debian 9, MariaDB, PHP7, NGINX, ISPConfig). But, I do not understand how to configure to work on SSL, since Sprutio's documentation is not good.

Below is the web link file manager:
https://sprut.io/en/install

Below is the Git link where there is a discussion about SSL:
https://github.com/LTD-Beget/sprutio/issues/65
https://github.com/LTD-Beget/sprutio/issues/70

Best Regards!