Force SSL for entire site

Hi guys,

I couldn't find previous post where it talk about this. I want to make my entire website secured, how do I do that?
I want it so that when people go to my website there is a lock icon where it says https:

I am using opencart Version 2.0.1.1

I tried using this code in the htaccess but it did not work:

RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://mywebsite.com/$1 [R=301,L]

(of course I replaced my website.com with my own website)

Can you help?

The code should work as long as you have a preceding
RewriteEngine On
and correct RewriteBase set
Also make sure that your RewriteCond in not mixed up with other conditions.
How does your .htaccess look like?