A Complete Guide to Switching From HTTP to HTTPS

Vladislav Denishev:

HTTPS is a must for every website nowadays: Users are looking for the padlock when providing their details; Chrome and Firefox explicitly mark websites that provide forms on pages without HTTPS as being non-secure; it is an SEO ranking factor; and it has a serious impact on privacy in general. Additionally, there is now more than one option to get an HTTPS certificate for free, so switching to HTTPS is only a matter of will.
I made the switch to HTTPS when I upgraded to a new Linux server this year. Much easier than I thought it would be.

This is a great comprehensive guide to do the same for your own website.