Where do I need to install the app (indexer or search head)?
What is the procedure for that?
Start here, with the documentation on AWS add-on:
https://splunkbase.splunk.com/app/1876/#/documentation
http://docs.splunk.com/Documentation/AddOns/latest/AWS/Description
Then once you have the AWS add-on setup you can install the splunk app for AWS, and/or configure cloudtrail:
http://docs.splunk.com/Documentation/AddOns/latest/AWS/CloudTrail
Where to install is covered in the documentation.
Start here, with the documentation on AWS add-on:
https://splunkbase.splunk.com/app/1876/#/documentation
http://docs.splunk.com/Documentation/AddOns/latest/AWS/Description
Then once you have the AWS add-on setup you can install the splunk app for AWS, and/or configure cloudtrail:
http://docs.splunk.com/Documentation/AddOns/latest/AWS/CloudTrail
Where to install is covered in the documentation.