From the spend portfolio nav click on airtime:
Click on any of the network providers of your choice
Enter the recipient's number or choose a contact from your device, then click continue
Select the data bundle you want to purchase
Click on the continue button then select Naira as the payment method
Enter your 4-digit passcode for security reasons
To continue click on the confirm purchase button
Once payment is confirmed you will see a pop-up message that shows “ Your MTN data purchase was successfully completed”.