To forward your visitors to your new domain, first of all, you should park the old domain and then redirect that domain to your new domain.
You can get this done by inserting these code to the .htacess file under the public_html folder:
Options +FollowSymLinks RewriteEngine on RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L]
Don't forget to replace www.newdomain.com in the above code with your actual domain name.
In addition to the redirect, we suggest that you contact every backlinking site to modify their backlink to point to your new domain.