There are two different ways to change the URL of your Facebook page depending on whether it is a profile (for personal) or page (for businesses).

How to change your Facebook URL for a profile

Step 1:
Head to your Settings & Privacy that’s located in the top right of your Facebook page under the drop down menu

Step 2:
Then click on Settings in the next menu

Step 3:
In General Account Settings click on the pencil next to the field that displays your Facebook URL

Step 4:
Enter a new Username, and make sure your new username is available.
Once you’ve entered an available username, click Save Changes

How to change the Facebook URL for a page

Step 1:
You must be logged into the admin account linked to your business page to do this.
Head to your Facebook business page and click on the About section

Step 2:
Click on Edit Page Info in your About section

Step 3:
Enter the new name into the Username field

Step 4:
This will automatically save your changes once you click outside the Username field if the new name is available