This guide will serve as a step-by-step basis for setting up the gm48.net Leaderboards for your game entry.
It will not go into detail on how to install the individual programs, applications and scripts, but instead serve as an overview of the process at large.
Set up and enable the YoYo Compiler (YYC)Please read this YoYo Games guide: https://help.yoyogames.com/hc/en-us/articles/235186048-Setting-Up-For-Windows
The section "Some Package Types Require Visual Studio" is the most relevant here. They will ask you to install Vistual Studio Community. The latest version is OK to use. Install here: https://visualstudio.microsoft.com/
Once installed, open GameMaker Studio 2 and go to File > Preferences > Platform Settings > Windows and set the Visual Studio Location.
The path could look like this: "C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars32.bat"
When you have set the location, try and compile your game with YYC set as the Output in the Targets menu in the upper right side of the GameMaker Studio 2 interface.
Submit your game to receive API CredentialsYou should submit your game as a draft. Unlisted or private, doesn't matter. https://gm48.net/submit
Open the Leaderboards on gm48.net via Dashboard > (your game draft) > Leaderboards. This page will have the required information for the next couple of steps, so keep it open.
Install gm48.net OAuth2 for GameMaker Studio 2 in your game projectNot much to say here, but to follow the instructions here: https://github.com/tehwave/gm48.net-oauth2-gms2
Install gm48.net Leaderboards for GameMaker Studio 2 in your game projectSame thing, follow the instructions here: https://github.com/tehwave/gm48.net-leaderboards-gms2
Finish adding leaderboards to your gameThe only remaining thing is to add the leaderboards to game. You can create the leaderboards via the Dashboard and add scores to them via GML in your game project.
The scores submitted can managed via the Dashboard as well.
You can see the leaderboards for your game via its game page on gm48.net. Next to the Download-button, there's a Leaderboards-button that will pop up and show the scores and whom submitted them.