First login into my.roku.com and go to PIN Preference Option.
You can add a pin number to protect your Unauthorized transaction in the Roku.com/link account.
Whenever you want to add or remove channel in the Roku channel store, It will ask you PIN number, So if any other person will try to add any channel and if he does not know pin number he can not add any channel in your Roku account. It will save you money because Roku will not give you any refund even you mistakenly bought any channel.so basically it is a security feature.
In the PIN Preference option click on Update now it will prompt you three options as…
1. Always require a PIN to make purchases and to add items from the Channel Store.
2. Always require a PIN to make purchases. ( Generate Roku Pin | go.roku/pin |)
3. A PIN is not required to make any purchase or add any item from the Channel Store.
So choose an option as you want but the best option is that choose option 1 so whenever you will try to buy anything or update anything it will ask you the pin number.
Now generate roku pin your 4 digit PIN number and after that, it will ask you for verifying so type again same pin number and save it.
If you forgot your PIN number then you need to login to your roku.com/link account and go to option PIN Preference and update your new PIN Number form here.