I already have Minecraft on my PC and now I want to play it with the Oculus VR glasses, but I would have to buy Minecraft again, can I log in there somehow? And if so how?
Do you have the Java or Bedrock (from the Windows Store) version?
If you have the Java version, you can easily install the Vivecraft Mod and do not have to buy it again!
Vivecraft: http://www.vivecraft.org/
The Bedrock version is available free of charge in the Oculus Store!
Bedrock: https://www.oculus.com/experiences/rift/741306562635466/?ranking_trace=0_741306562635466_SKYLINEWEB_1VNxApiOX1ARajYEi
However, I prefer Java over Bedrock, because you can install mods and shaders, etc.