Install Splunk App for Salesforce using the below URL.

https://splunkbase.splunk.com/app/1931/

We can check the below

1. Apex Pages performance
2. Apex Classes performance
3. Detect Security Threats
4. Reports and Dashboards usage and performance
5. Trigger Chatter feed to a group in Salesforce

Check the below link for more information

https://www.splunk.com/blog/2015/01/21/splunk-app-for-salesforce.html

Note:
Make sure Event Monitoring is enabled.