An Ether futures contract is a tradable instrument for the purchase and delivery of Ether. Each futures contract, like Ether, has a unique set of contract specifications that are set by the futures exchange.
Ether futures trading is an agreement between a buyer and seller at a specified price in a contract that will expire on a specific date. Traders can enter and exit positions, long or short, any time before the expiration date in these financially settled contracts.
One of the advantages of trading Ether futures contracts is that Ether futures offer traders direct market access for speculating on the price movement of Ether; traders can easily go long or short with good liquidity virtually 24 hours a day, and with lower trading capital requirements. This offers traders more opportunities and trading flexibility over buying and holding Ether in a digital wallet.
Ether futures are traded on the well-regulated CME Globex exchange where orders are matched and cleared on a fair and level playing field with full price and order transparency. Traders can place buy and sell orders through their broker to enter or exit a position virtually 24 hours a day. 
Yes, you can trade Ether futures with NinjaTrader. NinjaTrader is an industry-leading futures broker offering low commissions, low margin rates, and safety of your account funds. With NinjaTrader, you get all the tools and help you need to trade dozens of the most actively traded futures markets in the world including Ether futures contracts. 
Like every futures contract, the primary risk here is that the price of the Ether futures will go against the trader’s position. Ether news, supply and demand dynamics, and economic conditions can all have a significant effect on the price of Ether futures.
Ether prices can often exhibit periods of high and low price volatility, and these price swings can have a significant impact on traders. Ether buyers and holders have seen prices hit as high as $2,100 and as low as $1,100 this past year alone, and these are not nearly the biggest price moves over it's history. 
Micro Ether futures are cash settled and expired on the prior last trading day of the month before the settlement date. https://www.cmegroup.com/markets/cryptocurrencies/ether/micro-ether.calendar.html
Although the underlying technology the drives ether and Bitcoin are different, both micro futures contracts have similar margin and specifications and allow traders to easily trade long or short to speculate on the price or Ether. 
A Micro Ether contract allows you to control 1/10th of one Ether for as little as $200 in day trading margin or around $500 if you're going to hold the position for more than one day.  Traders should always hold enough trading capital in their account to cover price swings and losses.