How to Modifying app.config During Installation

Question

Hi Experts,
 
I am searching for a way to edit app.config connection strings using .msi file. Since it needs to be installed by other people. I dont want others to explicitly go into file and edit the server address and db username and password.
 
I want to have a nice interface or an .msi file would be a very good option. Can someone guide me with a starting point on this issue.
 
Your help is highly appreciated.