To redeem codes, you will first want to load Rocket League and head on-over to the "Options" menu. From here, you need to click on "Extras" and select "Redeem Code". See below: ...

If you’re looking to score some free customization items in Rocket League, you’re in the right place. Every now and then, Psyonix releases special codes that unlock free decals, banners ...

As mentioned before, to use redeem codes in Rocket League Sideswipe, you need to find the secret menu, follow these instructions for how to find it, and enter a redeem code.