If the scenario is that you have an idea to set up multiple websites but only want to have one admin panel, then you have to take a look at WordPress multisite.
So what is WordPress multisite? It is simply a network of websites that you can manage from one WordPress admin. By default, WordPress has not enabled the multisite feature. This can simply be done by some code in the wp-config file and .htaccess file.
You simply start by following the WordPress guide here https://codex.wordpress.org/Create_A_Network
When you are finished, there are some things you have to do in the Cpanel to get the subdomain to work on your new multisite. This means that you have to have access to your hosting accounts Cpanel.
Now we are going to add a wildcard to your domain, this is for getting your multisite to work after adding a new site.
First login to your Cpanel, then go to domains and add a new subdomain. The new
subdomain should be like this *.yourdomain.com.
In the Subdomain filed you just type *
In the Domain field, you choose the primary domain to your multisite.
And now this is IMPORTANT!!!! In the Document Root, it should only be this entry public_html/
If WordPress should recognize where the new multisite is it has to point to the «master» install Root of your WordPress multisite installation and not to own folders.
Now that you have created the wildcard subdomain the next thing you have to do is to navigate to Advanced Zone Editor under Domains in Cpanel. Choose your domain in the drop-down field, then find your wildcard record end press edit.
Now change the Type from A to CNAME and set the Adress to your primary multisite address (not IP just the address as yoursite.com)
Now you are ready to go, your site and domain are set up to work with your multisite.
To test it go to your multisite admin and make a new site and test if you can go to the site in your browser. The new site you have created uses a subdomain this you can change to another domain later as described on the next page.
The next challenge is to add a whole new domain to your multisite.
This means that you can have a unique domain on each of your multisite.
The first thing you do after buying a new domain is to point it to the same IP address that your primary domain has.
Next login to Cpanel and go to Domains and Aliases. Go and create a New Alias by typing in your new domain.
After adding the new domain check if the Doman Root is /public_html. Now you are done in Cpanel, go back to your main WordPress install and go to the site you have created and replace the subdomain into your new domain. Rember to save and you are ready to go.
Go on and test the site to see if all is working.