After a lot of research, I found my own solution...
First add a reference to System.Configuration
and then add the following code in the installer class
Assembly service = Assembly.GetAssembly(typeof(ProjectInstaller));
string assemblyPath = service.Location;
Configuration config = ConfigurationManager.OpenExeConfiguration(assemblyPath);
KeyValueConfigurationCollection mySettings = config.AppSettings.Settings;
processInstaller.Account = (ServiceAccount)Enum.Parse(typeof(ServiceAccount), mySettings["Account"].Value);
I am just so happy right now!! :)