Here is our tutorial...
Step 1. In the toolbar go to Toolbox → ModelMaker and open the folder where you have stored the model. For example , you may use the METRIC model (MappingEvapotranspiration at highResolutionusingInternalizedCalibration).
Introduce the data for Absolutecalibrationgains, which is obtained from the metada of the imagery. The bias can be set to 0.
In order to obtain the reflectance *if you need it, the image that you will use it the one that has already been radiometrically calibrated.
To obtain the d2 (distance Earth-Sun) you should consider the date and adquisition time of the image. SZ is calculated using the sun elevation angle, which you will find in the metadata of the image. The ESUN (exoatmospheric solar irradiation) is obtained from table for this sensor.
Once the model is executed, the result would be two images, the first radiometrically corrected, and the second with the reflectance calculation, which will be the one that should be used for the calculation of band indices *NDVI, NDSI, etc.
Credits go to Carola Buitron.