How do I add a call-to-action button to my Facebook Page?

Calls to action buttons help drive people visiting to your Facebook page to take actions that are important to your business. These Call to Actions or CTA's lead people to your website. Facebook provides you CTA options such as Book Now, Sign-up, Use App etc. You can choose from these accordingly and lead people to a particle page of your website. You can add a call-to-action to your Page at no cost. 
To add a call-to-action button to your Page:

1. Go to your Page’s cover photo and click Create Call-to-Action.

2. Choose your call to action from the drop-down list provided.

3. Provide the destination URL that you want to link to. Facebook will automatically choose the best destination based on your specified web address, but you can edit these suggested destinations.
4. Click Create.

Voila! You have created your Call to Action for your Facebook page in three simple steps. Once you've created a call-to-action button, you can track the number of people who have clicked on this button.