Usually when you car doesn't want to start and it makes a clicking sound it's usually due to a dead battery or low battery, a loose connection to the battery or starter. Could be corroded battery terminals or the solenoid on the starter or the starter itself.
Try checking the battery connections first for any corrosion. You can use baking soda to clean corrosion from battery terminals.
Then get your battery charged up or have someone try to jump start your car. If it starts after charging the battery or jump starting then you battery needs replacing.
If it still doesn't start then you might need a new starter.