This doesn't seem like a Splunk specific question, if you don't know how to forward logs to splunk, I would recommend learning the basics of Splunk first before trying to implement anything. There are many different aspects to Splunk that are to be considered before implementation, i.e. are you self-hosting or going to use Splunk cloud? Will you be running a Splunk cluster or just single instance that performs all roles. This is not a question to be answered here but rather one that requires more investigation and thought.

To answer your question regarding Kubernetes to Splunk, yes it's possible, a quick google shows this Splunk app will gather the data you need: https://splunkbase.splunk.com/app/3743/ .