Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^dwhs.com [nc]
rewriterule ^(.*)$ http://www.dwhs.com/$1 [r=301,nc]

This will redirect dwhs.com to www.dwhs.com (change dwhs.com to your domain name)

Step by step for DWHS Customers:

1. log into your cpanel: www.your-main-domain.com/cpanel/
2. Click file manager and click the option to see hidden files
3. Make sure your in the folder public_html or www
4. Then create a new file called:  .htaccess
5. Then in edit that file by adding this code:

Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^dwhs.com [nc]
rewriterule ^(.*)$ http://www.dwhs.com/$1 [r=301,nc]