If you use cpanel, the easiest way is i believe located at "manage autossl" or "manage autossl hosts".
In one of them you can generate free cpanel signed ssl certificates by running auto ssl for the site in question.
1) Then in your admin settings, update your list url from http to https
2) also admin settings -> button settings: same thing update all button path's to https
3) You need to run a few mysql queries to update member banners/mp4 etc.
You can do so by logging into phpmyadmin, select your database, then SQL tab at top
Code:
UPDATE `VL_sites` SET `banner_url` = REPLACE(banner_url, 'http://', 'https://');
UPDATE `VL_sites` SET `premium_banner_url` = REPLACE(premium_banner_url, 'http://', 'https://');
UPDATE `VL_sites` SET `mp4_url` = REPLACE(mp4_url, 'http://', 'https://');
UPDATE `VL_sites` SET `premium_mp4_url` = REPLACE(premium_mp4_url, 'http://', 'https://');