Serial keys are intended for PC and Android accounts only and are unable to be redeemed on Apple iOS devices.
Players on Apple iOS devices should purchase campaigns and add on items through the in-game store on the mobile client.
If you have purchased a Guild Wars Reforged serial key and have an existing Guild Wars account, you will need to add the serial key through the PC client, or through Guild Wars Reforged Mobile on Android.
If you are playing on iOS and do not wish to create an account for PC, you may request a refund by contacting support.