links don't work when www is entered

Greetings,

I am developing a landing page and want to use the app to redirect links from a wordpress page to the landing page.

For instance

https://mywebsite.com redirects to landingpage.mywebsite.com

But with the www added it only links to the blank wordpress page. Any way to assist.

Hope it helps.

https://www.ads-software.com/plugins/page-links-to/