How to add Master Card to Promote Page or
Boost Post in Facebook (android app)
Login into your Facebook account and choose More button
Choose Ads Manager
Choose Billing
Choose Add Card
Fill your Master Card details (Card number, expiration date, CVV) and press Save button
Here is an example:
To promote page or boost post choose Create Ad
Choose a page you want to promote
Choose desired option (Promote website, Promote page, Boost post)
Set up details and choose your budget
Choose Promote

You can get free Virtual MasterCard following instruction