M,
Yes you can monitor those logs files inside of Splunk Light. I'd suggest reviewing the documentation on getting data in (you can either monitor the directories that those files sit in or forward those files into Splunk) as well as look at this video on basic search in Splunk because you will use search to find those occurrences of "Warning". If you have the paid version of Splunk Light you can also setup monitoring and alerts to proactively tell you about occurrences of "Warning".
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