Basic Set-Up Help…

I’m still learning PHP and as silly as I’m sure it sounds, I’m struggling just to implement this plugin. I’m wanting the countdown clock to show up on a page, and I’ve tried implementing the shortcode “[fergcorp_cdt]” both in my HTML and in the page’s content, but neither have worked.

Can you send me the simplest step-by-step instructions on how to implement this with the exact code and syntax I need to use and where I need to put it?

I’m sorry for the trouble! Still learning! Thank you!

http://wordpress.org/plugins/countdown-timer/