Follow this guide to update the domain name of your Magento install. It's a good idea to back up your website prior to doing this.
- In cPanel, find the "Databases" section, and click "phpMyAdmin".
- Select your Magento database from the menu on the left.
- Select the "core_config_data" table.
- Find the "path" fields called "web/unsecure/base_url" and "web/secure/base_url".
- Select the pencil icon for each row, and change the value to the new domain name.
Note: Magento will not work with temporary URLs. If you are trying to test out your site before going live, the best way is to set up a subdomain for testing.