If you have never deposited fiat on to a broker exchange, then you will more than likely need to make at least one deposit first. Coinbase can be more convenient and safe for beginners, whilst LocalBitcoins allows you to remain anonymous and sell at a higher price. After the transaction is processed, the Bitcoin ATM should expel the requested money immediately or it may ask you to click on a Redeem Ticket option and scan your paper receipt that you were given.