After you get the API information all you need to do is: fill the information in your Miiduu administraion->Settings->Payments-?PayPal Express to enable it.
The shoppers can use the easy way to pay for you now!
Step 1: The shoppers can choose pay with 'PayPal Express' directly in the shopping cart.
Step 2: Login to the PayPal account.
Step 3: Go back to your Miiduu store to choose the shipping method.