Same question as I ask some other, who only uploaded for mac:
Do you have a Windows build for your game?
If yes, you can upload it on Google Drive or something and drop the download link here, if yo want to.
idk but suddenly when i upgrade to unity 2018 there was only mac os build.
also i only have like 30 mins left. /:
If you use Unity Hub, you can add more OS' for which you can build.
Just click left on "installs", then the 3 dots on your Unity version and then add modules.