It's no news that our banks have banned international transactions on ATM cards (aliexpress customers will understand this) , so we are limited to buying things i
n Nigeria only,there is always a way out.

Here are the steps to follow to get a free payoneer dollar Mastercard

http://www.techknow.com.ng/2017/02/how-to-get-dollar-mastercard-atm-for.html

Is it link to our naira bank account or we still source for dollar at black market rate and how do one fund it?

Its an account on its own. You fund it like a normal account. See more at http://www.techknow.com.ng/2017/02/how-to-get-dollar-mastercard-atm-for.html?m=1

And you don't have to go to black market to buy dollars. You can actually get lesser than parallel market rate from holders of some payoneer dollars.