https://docs.splunk.com/Documentation/Forwarder/8.2.1/Forwarder/HowtoforwarddatatoSplunkEnterprise
"You can collect data on the universal forwarder using several methods. Define inputs on the universal forwarder with the CLI. You can use the CLI to define inputs on the universal forwarder. After you define the inputs, the universal forwarder collects data based on those definitions as long as it has access to the data that you want to monitor. Define inputs on the universal forwarder with configuration files. If the input you want to configure does not have a CLI argument for it, you can configure inputs with configuration files. Create an inputs.conf file in the directory, $SPLUNK_HOME/etc/system/local