One thing at a time.
In the faq how do i forums gizmo has a basic island blurb that explains how to add to a island for say your site map island. https://www.ubbcentral.com/forums/u...Tips_for_Editing_Custom_.html#Post227829

Or you can see my question on the subject at https://www.ubbcentral.com/forums/ubbthre...html#Post227815

As far as a custom page Gizmo again has just posted what is called a wrapper mod. Which is a lot easier that the sample include file that comes with ubb. It is very simple to install and you really don't need to modify the ubb code. https://www.ubbdev.com/forums/ubbthreads.php/topics/318048/7_x_UBB_Wrapper.html#Post318048
All you do is upload about 4 files. And add your html to your custom page. It has some other items to address such as title but it is extremely easy to add a page with the same format as your ubb site.

Blue Man Group
There is no such thing as stupid questions. Just stupid answers