You bought the security, then you wrote a call option say for a month. Sold it with a premium. If the price gone up the counter party will exercise the option so you will remain with the premium. If the price went down the other party won't exercise and you will have the premium and the security.
According to this plan (100% coverage is assumed) you will not make a loss other then the loss from profit. But your gains will be limited with the premium. So the premium is important.
Good way of getting some extra from your investment.
But the option price shouldn't be one that will be easily exercised I guess?