the required software and arduino drivers.
The required software would include the Arduino IDE and your sketch. The Arduino folks make it each by hosting a number of files for various operating systems. You would have to copy and distribute each of those files, for every conceivable OS that Arduino supports.
Your install program would need to figure out what operating system was present and install the appropriate version of the IDE.
It would be better if you simply provided links to the Arduino (and other) site(s), and had people download and install the IDE (and any required user-contributed libraries) themselves. Then, all you need to distribute is your sketch.
For example i am creating a board when plugged into their computer using the USB port, should inform the user about the room darkness level.
If this is a custom board, just upload the sketch prior to delivery.