What workflow do you recommend to learn about Add-ons?

Hi, I am new to Add-Ons. I used it to install some files from Matlab Central. I want to learn how to build the models by modifying the ones I downloaded while keeping the originals. What is the best way to do this? I guess it may be better for me to make a copy of the folders and store them somewhere. Not sure where that somewhere should be as I read that I should place the files in some kind of Matlab path. As I recall, Matlab gave me some error messages saying that I had files of the same names, etc. Any suggestion?