Update Template for Website

Our Church is currently in the process of setting up a 3rd party management system. It is hosted in the cloud and can be accessed either by going directly to the website of the 3rd party or by implementing a username/password login box on our site. I have the code to insert, but do not know how to edit the template in put it in. Our website is [login to view URL], and I would like to placed on the right under the 'Extra Info' menu. Ideally it would only appear on the home page. Hopefully will be a short, simple task. Thanks