Replacing Calender with IFrame?

I am new to the Drupal world, and website maintenance. I do have a technical background though....

I currently have a Weekly Calender on my site.... we are looking to replace the current calender page (leave the main redirect button as it is) with a iframe.
I have the iframe code that is needed to drop in place, but i need to know where and how to do this on the drupal menu.
I don't want to screw anything up.... but, don't feel i need to get our old programmer involved either.

I am basically looking to replace the webcontent with the code for the iframe.

Any help would be greatly appreciated.