Overview

Having a fully functional multiplayer game? Chances are, you want to release it on Steam. And you want to benefit from Steam's API, for example, by using its lobby system, instead of punching NAT holes. I will give you an overview of the process before you start it yourself:

1. Integrate Facepunch.Steamworks to your Unity Project
2. Push your Unity Project to Steam and have proper Steam overlay
3. Connect Facepunch logic with Forge's

Now, do not rush this. You will escape a lot of headaches. Since this is an overview, I want to post the resources I used, to get a full steam release. Read/Watch these when in doubt.

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The OG working Forge-Steam example. Clean and perfectly working lobby, mixing Forge and Steam. https://github.com/phalasz/forgesteamworksexample

The Steam API It includes the latest Steam SDK. Just follow the instructions, aka copy-paste it on your project, and write the code it says, on appropriate gameobjects. https://wiki.facepunch.com/steamworks/Installing_For_Unity

Original/Raw installation, of Steamworks.NET (NOT FACEPUNCH!!) It is good to see how it originally works, with steam_app_id etc etc https://www.youtube.com/watch?v=o5-Y-5Dtg_c

Uploading to Steam&Managing Builds (using Steamworks.NET, not FACEPUNCH, but the process is the same pretty much) https://www.youtube.com/watch?v=rK5Fr5hhslM