All you have to do to point your website to a "Coming soon" page is create a simple index.html file in your web hosting account's main folder (usually public_html, www or httpdocs). The index.html file should contain the following code:
<html> <body>
Coming Soon!
</body></html>
The above instructions are for pointing a primary domain to such a page. In case you are pointing an addon domain the file index.html has to be created in the webroot of the addon domain. Such a page cannot be created for parked domains.