The article outlines to process of changing the PHP version currently being used by your cPanel hosting account.
1) Login into your cPanel account via your client are as outlined in the article here or if you have your cPanel credentials simply go to the URL http://yourdomain.com/cpanel. Note: Replace yourdomain.com with your actual domain name.
2) Once logged into your cPanel account navigate to the "Software" section and select "MultiPHP Manager" as outlined below.
3) On the following page click the check box next to the domain on your account you wish to change the PHP version for, select the desired "PHP Version" in the drop down, and lastly click the "Apply" button.
Note: Making this change will make your website inaccessible for 1-5 minutes displaying a generic 504 gateway timeout error while the server is making the required changes in the back end. If this issue does not clear up withing said 5 minute window it likely means that your website code is not compliant with the new version of PHP.