How to handle nighttime potty training

The term 'nighttime potty training' is actually incorrect. You can't train overnight the way you can during the day. During the day, you can leave your child in undies and endure some accidents while they learn the feeling of needing to go to the bathroom before it happens. 

But, the brain-bladder connection that need to be made at night is different and may take weeks, months or even years longer to "click." At night your body has to recognize the feeling + wake the body up in time to make it to the potty. It's different and more complicated than daytime potty training which is why it often takes longer. 

The best bet is to leave your child in pull ups until they are dry overnight for 2 solid weeks. Once you see that, try overnight undies. 

Your child may wake to go potty sometimes but they should be able to sleep 10-12 hours without needing to wake to go potty.
If you find that they're waking frequently, you can try limiting liquids to hour or two before bed - just make sure they're not chugging right before bed.