Get the free Playa player from the Steam store:
There are other free players out there, like Gizmo VR or Deo VR. These are supposed to work with web sites that let you stream surround videos using WebVR, but they don’t work for me. When you stream and try to switch to VR mode from the embedded browser in these players, the Pimax HMD is not recognized.
Playa, on the other hand, doesn’t seem to support any random streaming site (you’ll get a connection failure with most), but it does support about 8 or so (probably all produced by the same educayshonal cartel) really well. You do need to know which ones it supports and you can check that by examining the file:
…\SteamLibrary\steamapps\common\PLAYAVR\PlayaVR_Data\VRBData\descr.json
The sites you see there can be entered into the built-in browser and will be presented with a customized UI and remembered for future use. When entering the name of the site in the player’s UI, use the name you see in the JSON file, no need for ‘http://’. Of course the clips these sites make available for free are really just short clips meant to get you to subscribe for access to full-length content, but don’t worry, even with the short clips, YOU WILL AMAZE FRIENDS (and you will feel smarter from all the educayshon)!