How can I configure SSL in my domain in a droplet with multi domains when I have one domain in use?

Hello DO community.

I am try configuring SSL for my domain (georodigues.com) this is a wordpress site and I am using Let’s Encrypt for that.

So, I am following this article to learn about this question: www.digitalocean.com/community/tutorials/how-to-secure-apache-with-let-s-encrypt-on-ubuntu-18-04

My situation is that:

1. I am using a single droplet on DigitalOcean for my personal sites;

2. In this droplet, I have one site works right now and this site are using a Wordpress (Apache, PHP, etc);

3. In the future (less them one month) I will install a new domain on this droplet;

I am reading this article to help me configure many domains in the same Apache, in the same droplet: www.digitalocean.com/community/tutorials/how-to-install-the-apache-web-server-on-ubuntu-18-04

My question is:

If I create multi domains structure in my apache server, what can I do with de main domain (georodrigues.com)? The domain that are works now.

Can I use the backup to restore the site? Or can I move the files to the folder correspondent (Eg: var/www/html/georodrigues, var/www/html/secondsite etc) before I made changes In apache setting? The site will works or I need to change other configuration?

If the community can help me with some tutorial will be very nice.

Thanks :)