A car that clicks when trying to start can be caused by a lot of different things.
But first make sure your battery is not dead by charging it up with a battery charger or have someone jump your car.
If that doesn't work then check your battery cable connections to see if they may be loose or corroded.
Sometimes a corroded battery cable connection can cause a car to click and not start and also when your battery cables and battery terminal connections are corroded the alternator won't be able to charge the battery up properly which could result in a dead battery.
The corroded battery cable connections can also cause your starter and starter solenoid to loose proper connection which will cause the starter to not get enough voltage and amps to turn the starter over.
You can clean the battery cable connection of corrosion by pouring baking soda and water over the battery terminal connections and dipping the battery cable terminals in some baking soda and water.
Use a battery post and battery terminal cleaner that has a wire brush on it to clean the battery terminals and battery posts and see if that fixes it.
If your battery is good and charged up and the connections are all tight then your starter or starter solenoid are likely bad and need replaced.