A call option has no value if the underlying security trades below the strike price at expiry. A put option, which gives the holder the right to sell a stock at a specified price, has no value if the underlying security trades above the strike at expiry.
In either case, the option expires worthless. When an option is in the money and expiration is approaching, you can make one of several moves. For marketable options, the in-the-money value will be reflected in the option's market price. You can sell the option to lock in the value, or exercise the option to buy the shares (if holding calls) or sell the shares (if holding puts).
Check with your broker to see how in-the-money options are handled at expiration. A broker such as Fidelity may automatically exercise in-the-money options on your behalf unless instructed not to do so.