Buy from trusted sellers: Roblox’s official store or big retailers (Amazon, Walmart, Target, Best Buy, GameStop) — either physical cards or digital codes.
If you buy a digital code, you’ll get a code by email; physical cards have a scratch-off code.
Redeem the code at roblox.com/redeem (log in first).
Safety tips: only buy from reputable stores, never share your code, and avoid unofficial websites/offers.
That’s it purchase, get the code, redeem on Roblox.