Unfortunately forcing your WordPress site to use HTTPS is not as simple as updating your .htaccess(in most cases) but luckily there is a very simple solution and in most cases you do not need to do anything other than install a plugin.
Assuming that you already have the SSL installed on your site, simply install the following plugin:
After installing the plugin, activate it. It will then prompt you at the top of the wordpress admin side, if you are sure you want to force https on your site in which you confirm. Below you will find a quick video demonstrating how to install and activate the plugin.
After following the video, your site should now load up using HTTPS, any traffic going to HTTP will be redirected to HTTPS. If not, feel free to open a ticket up so we can look into it further.
The other issue that may come about which we see more times than not, is when switching over to https, you may notice the green lock is missing from your browser, example:
when you should be seeing:
This is called having ‘mixed content’. Mixed content basically means, you are trying to load your site using HTTPS however you still have content in your code/database that is trying to load using HTTP. To learn how to resolve mixed content, please use the following article.