Does ECC RAM usually work automatically or do I need to configure it in BIOS?

Most motherboards that support ECC will detect it automatically and enable error correction without you touching a thing. The exception is some consumer boards that require you to enable “ECC Mode” in BIOS, which is rare on recent platforms but happens on older LGA 1150/1151 boards and some budget AMD boards. Check your motherboard manual’s memory section, then verify with CPU-Z or dmidecode on Linux. If it says “ECC Enabled,” you’re done — leave it alone.