There are two primary ways for collecting eye tracking analytics.
The simplest way to gather eye tracking data is to use Gaze data logging in the Varjo Analytics window. It will produce a video (AVI) and data (CSV) files from a Varjo Analytics window recording. You will be limited to the format and data available in the CSV file, but you do not need to do any integration to your application. This method can be used with anything running in the headset.
The advanced way of gathering eye tracking data is to use Varjo Gaze API directly in your application. With this you are in control of gathering the data and you can export it to any format you wish to implement. This API is available in Varjo Native SDK and in Varjo Unity XR SDK. This method can also be used to make an external application that is only gathering eye tracking data if you cannot implement the API directly to the application you wish to collect the data from. Eye tracking data is not available in OpenXR or OpenVR APIs.