It is not uncommon for Splunk servers to not have access to the internet, particularly in a data center. In this case, follow these steps:
- Download the app from https://splunkbase.com. The file will have a .spl or .tgz extension.
- Navigate to Splunk Apps, then to the Apps page.
- Click on Install app from the file.
- Upload the downloaded file using the form provided.
- Restart if the app requires it.
- Configure the app if required.
That's it. Some apps have a configuration form. If this is the case, you will see a Setup link next to the app when you go to Manager | Apps. If something goes wrong, contact the author of the app.
If you have a distributed environment, in most cases the app only needs to be installed on your search head. The components that your indexers need will be distributed automatically by the search head. Check the documentation for the app.