In order to buy Ethereum on Robinhood, you must first create an account with the broker. Once you have done so, you can then deposit funds into your account via ACH or wire transfer. When your funds have been deposited, you can then place an order to buy ETH. There are two types of orders that you can place: a limit order or a market order. With a limit order, you specify the price at which you are willing to buy ETH.
The order will only be filled if the market price reaches your specified price. With a market order, your order will be filled at the current market price. After your order has been placed, it will be filled and your ETH will be deposited into your account. You can then hold onto your ETH or sell it for cash.