If you have to enable the SSL support for your CMS you need to modify the CMS settings to make it responds correctly in https. This configuration is not provided by default and it requires a specific and different procedure depending on the CMS.
To enable https on WordPress , enter your Admin area and click on "Settings". You will see the address to which the website will respond and change the protocol from http to https. As you save the configuration you are immediately redirected in https.
Enabling the https connection in Prestashop is quite simple. Enter your Admin area and click on "Settings". Here, click on the icon "Active SSL". As you click on "Save" you will confirm the new settings.
If you use a Magento CMS , enter your Admin area and go to"Secure" section: here, you have the possibility to change your e-commerce's URL. Change the URL Base and select "Yes" to enable the options to use https both in the Front-end and in the Back-end and then click on "Save".
If you use a Joomla CMS, enter your Admin area and click on "System". Then, click on "Global configuration" and "Server". Then, you have to select the option "Force SSL" and click on the icon "Whole website". In the end, save all the changes to end the operation.