PayPal instructs to "enter the 4-digit code that appears on your card activity next to the charged amount." The problem is the 4 digit code is nowhere to be found. I tried twice, I logged on to check my statement, the code is nowhere in the description next to the charged amount.
Are you trying to add and confirm a debit card? If so then sadly you can't.
You can't add a local bank account / debit card in your country. You can only link a visa credit card.
Also the option to receive paypal payments is sadly not available in Nigeria. You can only send payments for purchases funded by your (confirmed) credit card.
Paypal varies a lot country to country and can only offer the services that the banks / governments of that country allow it to offer. There are quite a few countries unable to receive paypal payments.