To sell, you will first need to get an active price and then proceed to use this price to place an order. The getPrices query allows you to do this. You can also pass an optional cryptocurrency argument to view singular cryptocurrency prices.
The price call will return notable fields:
id: this is Global Object ID that you will need to pass to the sell mutation. You can also use it to retrieve a BuycoinsPrice node.
cryptocurrency: this is the cryptocurrency of the prices displayed
sellPricePerCoin: this is the sell cost per coin in Naira
minSell: this is the minimum amount of that cryptocurrency that can be sold
maxSell: this is the maximum amount of that cryptocurrency that can be sold
expiresAt: This timestamp is when that price will expire
To place a sell order, you will need the id of an active price.