@Klint hi
At first you have to deploy graph on your side. Few notes - looks like u must use separate deploy for separate contracts. A lot of docs there how to.
Then Galxe go and approve ur game. Inside Galxe you can use graph (chain agnostic) code to create events based on it (there are any logic can be injected in graph results).
Be sure that all of ur smart contracts have necessary events (graph works on top of it) with necessary properties.