Hi, I am guessing you mean a regular human treadmill right? First ALWAYS take your dog out to the bathroom BEFORE you go on the treadmill (I have heard some horror stories!! ew lol) . Start by getting your pup used to the treadmill, give it a name, make him get on it and reward him, don't turn it on just yet. on a human mill I tie a leash loose enough for him to be able to move back and forth, but not loose enough so if he loses his footing he will slid off the back of it. NEVER leave your dog unattended while on the treadmill.
I warm my boy up for 5 minutes slow walk, then run him for 10, fast pace walk for 5, run for 10 and then fast walk for 5 until I can tell he is done and wants to get off. Sometimes we go for an hour sometimes a half hour, depends on his mood and how he is doing. I put my boy on the treadmill to lose weight, so it depends on HOW much you are working your boy if you adjust his food. Are you just doing it for fun or for training? If its cold like around me in the winter you use the treadmill more and are outside less so I never adjusted my boys food.
Here is lesson one with my boy, I was slow, didn't want to scare him and just a constant reward and praise praise praise:
This is him more recently, no reward until he is done so he doesn't choke or anything while on it. My treadmill is old, this is on full speed, lol.
Hope that helped, let me know if you have any questions!