How to forward visitors to my new domain?
To ensure your new primary domain name is used, first park the previous primary one as shown in this article and then redirect the old domain name to your new one by inserting this code into the .htaccess file in your public_html folder (you can modify/create that file via File Manager in Site Tools):
Options +FollowSymLinks
RewriteEngine on
RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L]
Replace www.newdomain.com in the above code with your actual domain name.
In addition to the redirect, contact every backlinking site to modify their backlink to point to your new domain.