http:// vs http://www

sorry if I am making a post already exist. but I have couple of questions..
I made three aliexpress affiliate sites.
when I open the site , it comes like http . I have searched a lot online and many people mean that httpwww is better for SEO etc and google better recognize it and there was written a lot of things about backlinks should be linked correctly etc.
I have already three sites running , is it possible to change this http to httpwww . I am using godaddy hosting..or in future if I register another site, I just need to write www or httpwww??? hope you understand.
can someone please shed light on this.i appreciate it.

Yes you can add an ssl to your current sites to get the https in front of your domains. Just contact godaddy about adding it.

I was not asing about ssl but normal http vs httpwww when you tried to open your website..how can I add in wordpress so my site shows httpwww and then ....com

Google doesn't care if your site starts with www or not. Makes no difference.

Simply 301 redirect the non www to www using .htaccess. When building backlinks make sure that you use http://www.yourdomain.com/ instead of http://yourdomain.com/