I just installed this. There is a Readme.md in the file, that told me:

1. Copy defaults.ini to config.ini
2. Edit config.ini and delete any lines you do not wish to override
3. Do not delete the [globals] line
4. See http://selfoss.aditu.de/ for examples

Since I am the only user on my systems, I left the user name and password blank, so when I put the URL in firefox, I do not have to login to read my feeds.