in my Main -> Activity_Create I load a layout containing a tabView
On Tab one I load a form
on Tab two I load a customListView
I have created a separate activity module for my customListView, where do I add the code to automatically run and populate the list when the Main activity is started, or do I have to add a custom module and call a function from my Main -> Activity_Create method?
Not sure what do you mean with TabView. I recommend you to use TabStripViewPager.
The code related to the CLV must be in the Main activity or in a class that is initialized from the main activity. It cannot be in a different activity module.