How to Redeem a Nintendo Switch Online Membership

Go to this website: Visit the Nintendo eShop redemption page at https://ec.nintendo.com/redeem/#/.
Log in to your account: Sign in to your Nintendo account or create one if necessary.
Enter your membership code: Input the code for your Nintendo Switch Online Membership.
Redeem the membership: Click “Submit” or “Redeem” to activate your Nintendo Switch Online Membership.
Start enjoying benefits: Access online multiplayer, exclusive offers, and more with your membership.