[Install.]addFile

The Install object's addFile method is the standard way to queue files for installation.

 var xpiSrc = "file.txt";
 initInstall(
  "Adding A File", 
  "testFile", 
  "1.0.1.7", 
  1);
 f = getFolder("Program");
 setPackageFolder(f);
 addFile(xpiSrc);
 if (0 == getLastError())
	 performInstall();
else
	 cancelInstall();