Open the iPad - take out the battery - put the disk in - close the case - power on! (This is a joke - don't try it).
If you own the disk - you can use multiple programs (I will not name due to forum rules) to convert them into .mp4 format. This is the format the iPad will play. Of course, in order to convert you will need to be able to read the disk which may/may not be supported by your computer.