Module created, Could not access

I am beginner , I have created custom module using folder structures and relevant files, It is showing in the Module List But when I tried to access that module it says as :

Error: Module TestApp does not exist.

You should create modules through the Module Builder in Admin -> Module builder, not by copy and pasting files manually as this will cause various issues if not done correctly.



Thank You Will, So the module builder will create the basic structure and then we can customize as we want , right?

I have tried to create the module using the module builder . I created A Package and then I tried to create a module but the windows shows as in the picuture(Error is attached as Image File)?

Dear Will ,can you please help me to sort it out?