There is no official app from Google for local video yet, but VRTV does a pretty good job, so grab that from the Play Store.
In your Android Settings, disable NFC (found in "More" under Wireless & Networks). This will prevent the Daydream enviroment from launching when you put your device in the headset.
Download a video from WankzVR to your phone, remember the location where you saved it and don't rename the file.
Open VRTV and browse to your VR directory where the video is stored.
Set "Screen" to Dome 180, "Video Type" to 3D SBS, "Projection" to Normal. ,Make sure VR Player is selected for head tracking support, and click the play button.
Center the orientation as best you can and put the device in the headset.