Locate the asset tag on the unit and match the asset ID to the sensor you are claiming in the DT Installer. For guidance on the location of asset tags review Asset Tag Locations 

Clean and dry the surface, make sure no frost or ice is visible

Install the sensor inside on the left wall near the data plate.  Do  not cover the data plate.  Sensor should be at least 4 inches below the top of the door opening and at least 6 inches back from the front of the door opening.