How can I change the app for managing root access from SuperSU to Superuser? I used a rooting package on my Galaxy S4 which installed SuperSU. Howvever, I preferred to use SuperUser, so I removed SuperSU and installed SuperUser.

Now the apps that normally request root do not seem to do it anymore, and also cease to function correctly. 

How can I make my newly installed SuperUser App into the default root manager?
open settings in Super SU.
go to cleanup section. 
switch Superuser app.