If you're using a hosting provider then you need to pay your hosting provider to install it (basically include it in their nginx/apache config).
If it's a self signed certificate that you're creating then you're not going to have the green bar.
A free alternative to self signed is startssl (1 year expiry I think) or letsencrypt (60 or 90 day expiry, I can't remember, it was mentioned upthread).
Easiest option is to buy a certificate through your hosting provider that will cost a bit but be signed by Thwarte or whatnot.
I hope this post doesn't confuse you.
Are you following a guide?