config.json file is auto generated at first launch with a template.
You must configure it with two important values:
1- fooocus-directory contains the full path of your Fooocus installation
Note that you MUST double the \\ in each folder
2- fooocus-address contains the http address of Fooocus web UI. By default, the address is "127.0.0.1:7865" and should work
You must restart FoooXus app to take into account these file updates
The next part of config.json file is dedicated to illustration presets.
See this document to manage your illustration presets.