Clone SteamWrap from https://github.com/slameron/SteamWrap .
Run setup.bat/sh based on your platform and point it to your Steamworks SDK and hxcpp headers.
Run haxelib dev steamwrap path/to/your/steamwrap/clone in a command line
Add a file called Keys.hx to your source folder containing this code:
package;
class Keys
{
public static var steamAppID = YOUR_APP_ID;
}Replace any instance of YOUR_APP_ID in Keys.hx, project.xml, and appid.txt with your Steam game's app ID.
Build the game using your method of choice, making sure to use the -Dsteam flag, such as lime test windows -Dsteam.
On one client, press make lobby. It will default to friends only privacy with up to 5 members. You will be on a screen with a white square you can move around with WASD.
On another client, press join lobby. Join the lobby of the first client using the friends interface on Steam.
Both clients must be friends on Steam
Note: The second client will not see the square of the first client until it moves around