Initialize the telemetry/app insights agent by calling the "Init" client action in the ApplicationOnReady action of the entry point application by setting the agent configuration as input to the actions. 

"InstrumentationKey" is a required attribute for the agent to be provisioned. The configuration has a ton of options available that you may use to set such as auto telemetry (ex "autoTrackPageVisitTime", "enableAutoRouteTracking").

Refer to AppInsights Configuration for more details about the setting available for the initialization and API Summary for the other actions provided by the library.

Other references:

Configurations: https://github.com/microsoft/ApplicationInsights-JS.