Based on feedback such as yours we are working to make the Splunk Light forwarding documentation clearer and more self-contained. In the meantime, the following topics in the Splunk Light docs should provide the info that you need to get started:
Install and deploy a universal forwarder.
Receive data from a forwarder. In particular you might have missed the step in this topic about configuring your Splunk Light instance to receive data.
The process of configuring your forwarders as deployment clients is optional, but is required if you want to use the Add Data workflow in the Splunk Light user interface (instead of managing data inputs at the command line or config file level on each forwarder).
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