Step 1:
Visit the playstation website first, (https://www.playstation.com/), then click Sign In.
Step 2:
Enter your ID (E-mail) and Password, Click Sign in.
Step 3:
Hover over your profile, Click Redeem Codes.
Step 4:
Enter your 12 Voucher Codes, Click next to complete.
Redeem has been successful, Happy Gaming !