Install:

• Press the (+) button at the top left corner of the Package Manager and select "Add package from git URL...".
• Paste https://github.com/0lento/steamworks.net.git#unity-package.

Samples:

• When you select SteamWorks.NET on Package Manager, look for the Samples section on the package.
• Note that both Example and Test samples have script named Logger.cs so if you install both you can just delete the file from one sample to suppress the warning.

Disclaimer:

• This is a quick fork to make SteamWorks.NET run as upm package and is largely untested, no support for this will be given whatsoever. For original SteamWorks.NET, look at https://github.com/rlabrecque/Steamworks.NET