If the spot price of the stock exceeds the "strike price" in the
call option, the option is in-the-money and you can exercise it.
But if you have a choice, wait to exercise it until the stock's
spot price exceeds the strike price enough to cover the
premium.
Example: the strike price is $40 and the premium was $2. In
order to make money on this option, the stock price needs to be
over $42--enough to pay for the stock and replace the money you
spent buying the option.