You load up all the URL's in the program and it will show you what platform each domain is - I suggest you stick to the "one file for all results" option as that is the safest in case the program crashes in the middle (results are saved real-time into a txt file). A bit unwieldy though as the results are all in one file.
You will have to divide all the URL's you want to test into batches of 20k each as the platform reader tends to crash if you load up too many URL's at once.