How futures are sold, when they are first released?

Futures are not "things" to sell. When you "buy" or "sell" a future, you enter into a contract with a counterparty. So the exchange releasing a future just means that they create a record in their system of a particular futures contract. That's all. Nothing needs to be "created" other than that.

The market (not the exchange) determines the price of the future just like a stock - bid and ask orders are made, and market orders are matched up with the order book just like stocks in the secondary market.