Knowing their estimated costs and profit requirements the arbitrageur determines a minimum difference they need between the futures’ prices and the spot price before they will enter the market. They then monitor the price difference between Bitcoin futures and the Bitcoin exchanges and if large enough they act to profit on that gap.  For example, if a specific Bitcoin future (e.g., February contract) is trading sufficiently higher than the current Bitcoin exchange price they will short that Bitcoin future and hedge their position by buying Bitcoins on the exchange. At that point, if they have achieved trade prices within their targets, they have locked in a guaranteed profit. They will hold those positions until contract expiration (or until they can cover their short futures and sell Bitcoins at a profit).
Don’t invest blindy. There are people in this world who would sell a blind person a pair of glasses if they could make money. Those same people play in the cryptocurrency markets and use every opportunity to exploit less-informed investors. They’ll tell you what to buy or claim certain coins will moon, just to increase the prices so they can exit. Due to the highly speculative nature of the cryptocurrency markets today, a good investor will always do his or her own research in order to take full responsibility for the potential investment outcome. Information coming from even the best investor is, at best, great information, but never a promise, so you can still get burned.
The Funds may invest in a combination of forward currency contracts and U.S. dollar-denominated market instruments in an attempt to obtain an investment result that is substantially the same as a direct investment in a foreign currency-denominated instrument. This investment technique creates a “synthetic” position in the particular foreign currency instrument whose performance the manager is trying to duplicate. For example, investing in a combination of U.S. dollar-denominated instruments with “long” forward currency exchange contracts creates a position economically equivalent to investing in a money market instrument denominated in the foreign currency itself. Such combined positions are sometimes necessary when the money market in a particular foreign currency is small or relatively illiquid.
There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.