Everething you need to know is shown in this video. But if you're lazy like me, you aren't going to watch 17 minutes long piece of crap sooo you can follow this "manual" (yeah right down there)
1) Acquiring Shadow Warrior Classic
For this tutorial you're going to need a copy of Shadow Warrior ("ooooh reaalllyyyyy??"). You have to use the free gog.com version, wich is called Shadow Warrior Classic Complete. (It didn't work with STEAM version for me so... don't use it.) Once you've successfully downloaded and installed the game you can go to another step.
2) Installing SWP port
Now you've got a folder filled with Shadow Warrior somwhere on your PC (if don't know where, check the installator) and your task is to download the SWP Port. Open the file you've just downloaded, and copy everything from it to your Shadow Warrior folder. You can now start the game by "SWP.exe", wich now can be found in the Shadow Warrior folder, but that leads to another problem.
3) Crappy audio Fix
You've started the game and you can hear, that something is wrong with the sound (Lo Wang's voice). To fix this, you have to right-click "SWP.exe", select properties ---> compatibility ----> and set compatibility mode for "Windows Vista", and in the same window, you also have to apply the option "run the application as an administrator". This step will fix your audio problems.
4) Setting up EXPANSIONS (datadiscs - Wanton Destruction, Twin Dragon)
Now if you want to play original expansions you have to download the Twin Dragon from proasm.com. After downloading, just open it up and copy the "TwinDrag.grp" file to your Shadow Warrior folder. That's all for this step, because Wanton Destruction is already included (called "WT.grp").
4,5) [Not necessary] Setting up EXPANSIONS for Singleplayer
If you want to play these expansions through SWP, you have to make a shortcut (right-click SWP -> copy -> right click into a folder -> create a shortcut), and then right-click the shortcut you've created -> properties -> and add "-gWT.grp" to the end of the target for Wanton Destruction, or "-gTwinDrag.grp" for Twin Dragon. Without quotation marks! And don't forget a space between "...SWP.exe" and "-gWT.grp"!
Example:
5) Multiplayer finally!
You'll need to download the 32-bit installer of YANG and install it. Once you've done that, you can start it (try to type "YANG" in start, it will show up). It will ask you a few questions (answer is YES to all of them). And then windows with Ports and Nickname settings will appear. In the window "Source ports" select "Shadow Warrior" and locate the "SWP.exe" in SWP option. Example: F:\Shadow Warrior Complete\SWP.exe . In the nickname window just select your nickname. Now a server can be created in "Action --> Create a room" and people can join it in "Action ---> Join room manually".
6) Multiplayer with EXPANSIONS!
In Yang, click on "Settings", select "TCs and Mods" and add a new profile. I recommend to name it Wanton Destruction and click "add files" and select "WT.grp" in your Shadow Warrior folder. Do the same for Twin Dragon. Now while starting server, where you want to play expansion and NOT the default campaign, you have to select the expansion (WT/TwinDrag), and in the create server window add an argument "-gWT.grp" for Wanton Destruction and "-gTwinDrag.grp" for Twin Dragon. Without quotation marks!
7) [OPTIONAL][RECOMMENDED] Installing High Resolution Pack (HRP)
Installing HRP is the last thing. It is optional, but I highly recommend it --- I do not anymore, I started to prefer the old classic look (and trash bins look glitchy with HRP...). The pack can be downloaded from here proasm.com. Open the "SW_hrp.zip" inside, and copy the "highres" folder to your Shadow Warrior folder. Make sure that HRP is enabled in SWP.exe. If you don't like the new monsters models, just delete or rename folder "monsters" wich is located in folder "sprites" (in "highres" folder).
8) Mouse invert and other important settings
Don't forget to improve video settings, and turn on the mouse invert in options -> mouse. You can also change the size of your HUD, or decrease the size of crosshair.
My configuration file is downloadable here, and you can copy it to your Shadow Warrior folder.
Important INFO
To play multiplayer, this configuration (SWP+GOG VERSION) must be the same on every computer. If you set it up for the first time, you can now just copy the whole SHADOW WARRIOR folder and only install and setup YANG on every new computer. If you aren't going to play on LAN, you'll need to setup HAMACHI/ EVOLVE/ZeroTier, or forward ports on your router (if you have a public IP).