How do I keep a Parked Domain Name in the address line of a browser

Here’s my problem: I have parked LizSeymour.com on top of StageMagazineOnline.com (which already has 6 versions of WP in various subdirectories). I pointed LizSeymour.com to /sings in my control panel and WP opens right away when that Domain Name is used.

However…

When using any link within WP, the domain name switches to StageMagazineOnline.com (as you can see).

I followed poppacket’s suggestion and added this to my wp-config.php file:

$hostname = $_SERVER[‘SERVER_NAME’];
$hostname = str_replace(‘www.’, ”, $hostname);
if ($hostname == ‘lizseymour.com’) {
define(‘WP_SITEURL’, ‘https://lizseymour.com’);
define(‘WP_HOME’, ‘https://lizseymour.com’);
}

Unfortunately, when moving around WP, the name changes back to StageMagazineOnline.com/(and then the file names being used)

What am I missing?
How can this best be done?
Also… I will be adding MORE WP blogs to this main address, so it’s very important to keep the new Domain Name when people visit my various sites.

Thanks for your help.

Charlie

[Apologies to Poppacket for contacting him outside of this forum… I had trouble finding out how to add a new thread – it’s not listed on most of the pages.]