Here are the steps:

1. You just create an menu item to point to your contact form.

2. Obtain the URL of your contact form menu item. It will look something like this:
http://ongetc.org/joomla/index.php?option=com_contact&view=contact&id=1&...

3. Creat a content page and enter this code in the content
{mosmodule grabpage=http://ongetc.org/joomla/index2.php?option=com_contact&view=contact&id=1...}

Note: I replace index.php with index2.php from the above URL that I obtain earlier!

That's it!

Now that when you view your content page it will show your contact form in it.

You can see a working sample here: http://support.ongetc.com/index.php?option=com_content&task=view&id=288&...