The steps are very similar to the ones from: https://help.series.hr/en/articles/12482933-how-to-install-the-series-activity-tracking-script
Download the Appication Centres model.
It will be downloaded as a .rbxm file.
You can either drag-and-drop it in your Roblox Studio, or right-click on ServerScriptService > Insert > Import Roblox Model.
Select the downloaded model from your computer.
Ensure that the model is in ServerScriptService.
This is what the hierarchy should look like.
Insert your API key in "SeriesApplicationCentres", in the dedicated field.
Ensure you have HTTP Requests and Studio Access to API Services enabled in your game settings.