Your baggage allowance comes with your fare and is printed on your confirmation — Business Class two bags of 20 kg, Economy one bag of 30 kg, Promo two bags of 23 kg, each with 7 kg of cabin baggage.
Extra baggage and paid seats are not yet on sale online. Buying extra baggage before you reach the airport is materially cheaper than buying it at the counter, so it is worth calling ahead rather than waiting.