Even though putting training routines into practce can be difficult and tests the will of most who try the principle are usually simple. In this case understanding thet any time you go back to the cage or even acknowledge your puppy while he is crying is encouraging more crying, period. It is possible you may be trying to force the nap, the same problem happens to the parents of new pabies, but if you need him to nap for your schedule then you just have to be patient and ignore the crying. You can type "crying" in the Forum Q&A search box to review other member questions and the answers and here is a little more info:
Using the palace
For the first week or two the puppy should be in his crate, door closed if he is not actively engaged with your family. After this initial period you can go to using a small room (bathroom) or an attached play pen with the door left open. Many people try to go from the confined space of the cage to free run of the house and usually get frustrated with the accidents. Your puppy has to learn what you expect and how to comply. As he approaches 12-14 weeks of age and control over elimination is improving then free run can work. If you are to have him away from the crate you can also take the pad and tray with you.
The first thing to understand is that your puppy has probably never been alone before so his anxiety about that is expressed as barking. Usually that will improve noticeably in less than a week if you approach it correctly. Any time you go back to his area while he is barking you are encouraging that behavior. You have to ignore the barking and not go back until he has been quiet for at least 30 minutes or after he wakes up. Other steps you can take that may help is using a covered cage (it will still take several days to adapt), having the cage in an area where he does not see or hear you and using interactive chew toys such as Starmark Everlasting Treat, Kong Quest or Traxx, Nylabone Romp n Chomp or processed bones or antlers (Blue Buffalo). Having music or a ticking clock can also help. The most reliable solution is a second puppy but if that is not feasible try these other suggestions.