You would need to create a
- Template file (.tpl)
- Controller file (.php)
- Model file (.php)
- Language file (.php)
All files are named the same with different extensions and located in their respective folders
You will also need to add more columns in the database named with the additional settings you ant to store.
In addition to your page specific setup you will also need to add a link to your page in the header file, in the menu.
You will use the model file to insert, update and delete data within the database. The controller controls what functions within the model are used.
Once created, In admin/ user group permissions you need to give access o the new pages
Take a look at the existing files to see how it works. Make a copy of one of the more simpler 4 files, rename, then start to modify them.
If you only want to add more settings to a existing page then you can add them to the existing 4 files and add columns in the database.
Hope that helps get you started, Good luck!