Nintendo Switch Online UK

Redeem on a Nintendo Switch Console
From the HOME Menu, open Nintendo eShop.
Select your user profile.
Scroll down and choose Enter Code, or navigate to Nintendo Switch Online → Redeem Code.
Enter the 16-digit code (letters and numbers only, without hyphens).
Confirm and follow the on-screen instructions to complete redemption.

Redeem via a Web Browser
Visit: https://ec.nintendo.com/redeem
Sign in to your Nintendo Account.
Enter the 16-digit code and click Redeem.