How to redeem a PlayStation Store voucher on a web browser

Go to PlayStation Store and click on your Avatar at the top of the screen.
 Select Redeem Codes from the drop-down menu.
 Carefully enter the code and select Redeem.
 The credit or content is now applied to your account.

How to redeem a code on a PS5 Console

Go to Settings > Users and Accounts.
 Select Account > Payment and Subscriptions > Redeem Codes.
 Enter the code and select Redeem.
You can also redeem a voucher code during checkout by selecting Redeem Codes and Gift Cards from the payment method menu.

How to redeem a code on a PS4 Console

Go to PlayStation Store > scroll to the bottom of the sidebar > Redeem Codes.
 Carefully enter the code and select Redeem.
 The credit or content is now applied to your account.

How to redeem a code on a the Playstation App
Select the PlayStation Store icon and then select the menu from the right side of the screen. 
 Select Redeem Codes. 
 Carefully enter the code and select Next to continue.
The credit or content is now applied to your account.