In the root folder of your website, delete the config.toml file that was generated by Hugo. Copy the *.toml config files from the theme into your config/_default/ folder. If you installed using Hugo Modules, you should not copy the module.toml file! This will ensure you have all the correct theme settings and will enable you to easily customise the theme.
Depending on how you installed the theme you will find the theme config files in different places: