Log in to your PrestaShop dashboard.

Using the top menu bar, hover over the Preferences tab and click on the SEO&URLs option from the menu.

This leads you to the SEO & URLs configuration screen. Scroll down the page until you find the Set Shop URL section. Here you will find the two URLs you will need to change. Shop Domain is the normal URL and SSL Domain is the URL for using the secure version of the site. Unless you have a custom setup, these will typically be the same.

After entering your new URL, click on the green Save button in the upper right corner of the screen. This will finalize and save your new URL.