how to use my coins?

Hello I just bought coins, but I can not complete the purchase because it asks for "discount code" and I do not know where to get that. please

Discount code is optional. You don't have to enter anything there if you don't have a discount code.

asks me to wait at least three days to be able to buy an article

If you want to buy from Trade section, you need 2 step authentication active for at least 3 days.