Hi @mela501 and thanks for your query. We have produced an extensive tutorial covering how to get up and running in using the Unity for Desktop SDK in conjunction with the Tobii Trackers @ https://developer.tobii.com/pc-gaming/unity-sdk/getting-started/
Whilst we hope to fix the SDK to support the latest version of the Unity Engine, for right now try using at most version 5.3.7f1 in conjunction with the steps we provide and kindly let us know how you get on. Best Wishes.