You say you put him out at night. Does he go? If not take him out a few times until he does. When he does try to associate whatever words you wish to the task. I've always used "puppy boo boo", and praise the dogs when they make one using those words. Then later when you take them out tell him to make a "puppy boo boo". I know it may sound crazy, but it works! Same for "puppy wee wee".

In addition to all the Karen has posted, one other thing you need to try- no food after 8 PM. Mine have been on free choice, and a couple of times they gobbled down a ton of food at 11 PM, and then couldn't hold it. Taking away all food after 8 PM solved the problem. If 8 PM doesn't work, then feed or limit food earlier. If nothing goes in, then nothing can come out.