Steam is required to run OpenVR applications, so install Steam and SteamVR. Once SteamVR is working properly with your headset, add OpenVR to the list of supported SDKs (see below to learn how to do this). If you require additional functionality beyond Unity’s built-in support, see the SteamVR asset store package.
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.