Final answer:
The command to add a license to the License Master in Splunk is 'splunk add licenses' followed by the license file path, typically executed with proper administrative permissions.
Step-by-step explanation:
The command used to add a license to the License Master in a Splunk environment is typically executed within Splunk's web interface or by using the command-line interface. To add a license through the CLI, you would use the 'splunk add licenses' command followed by the path to the license file. However, it's important to ensure that you have the proper administrative permissions to perform this action and to follow the specific procedures outlined in the current Splunk documentation, as the steps may vary depending on the version of Splunk you are using.