After you launch Stud Jump Simulator in the Roblox app, you can follow this step-by-step instructions to redeem your free reward: Click the Codes button (blue book) on the left side of the screen.

All players can now redeem the latest Jump Stars codes to claim free rewards.

This is only an overview of what Roblox Don't Press the Button has to offer, as it has more than 160 levels apart from the aforementioned ones.