Your configuration is passed down to the client initialization. (e.g: `createClient(config)`). The implementation is based on the package `pkgcloud`. You can read the docs [here](https://github.com/pkgcloud/pkgcloud#storage).
See the [using a provider](https://strapi.io/documentation/developer-docs/latest/development/plugins/upload.html#using-a-provider) documentation for information on installing and using a provider. And see the [environment variables](https://strapi.io/documentation/developer-docs/latest/setup-deployment-guides/configurations.html#environment-variables) for setting and using environment variables in your configs.