Following several good help links

A complete one that works.
It links to a github project on this topic.
At this moment, I am stuck with scenario that the app works 
independently, but does NOT work once I put it as one of the tabs. 
And, ultimately, it is the case how to separate into separate files.
Here is a post on modulize the app
The links an example of theRShiny output a modoulized way.

In order to modify the current Signature Analysis app, I need to re-visit Rshiny basic

I am reading this tutorial to refresh my knowledge.