Open the scene and hit play, you can then use WASD controls to move around. In the SampleScene you can enable the Auto Move property on the Cockpit object. You can also change the panorama ID on the Panoid proeprty on the PhotoSphere object.
Clone the repo ( or use the unity package in the releases) into the Assets folder in your unity project.
Add the Sphere.prefab to your Scene. You can change the Panoid property on the PhotoSphere component on the Sphere.prefab to any you like.
To get the Panoid from a street view page url:
https://www.google.nl/maps/@52.239981,6.851849,3a,90y,324.71h,64.65t/data=!3m5!1e1!3m3!1sFEpIJhSgOzoAAAQJOQCL3w!2e0!3e11
After the !1s and before the !2e is the Panorama ID, so here is it:
FEpIJhSgOzoAAAQJOQCL3w