[Kailynn]

For the contact us page you should create classes/XLite/Module/XC/CustomSkin/Controller/Customer/ContactUs.php with the following contents and then enable Custom Skin module (or redeploy the store if the module is enabled already):

 <?php

namespace XLite\Module\XC\CustomSkin\Controller\Customer;

/**
 * Decorated controller class.
 * 
 * @LC_Dependencies ("CDev\ContactUs")
 */
class ContactUs extends \XLite\Module\CDev\ContactUs\Controller\Customer\ContactUs implements \XLite\Base\IDecorator
{
    /**
     * Get meta description
     *
     * @return string
     */
    public function getMetaDescription()
    {
        return 'Your custom meta description for pages handled by this controller class';
    }

    /**
     * Get meta keywords
     *
     * @return string
     */
    public function getKeywords()
    {
        return 'Your custom meta keywords for pages handled by this controller class';
    }
}

For other pages you should create similar files, but with a different location/namespace/name of the class being extended. Also, you need the @LC_Dependencies only for controller classes that are added by modules (change it in accordance with the module name), for core classes skip it.