There is only way to approach that, you have to walk away and not go back unless she has been wuiet at least 30 minutes. Any other response encourages more crying. Here is some additional info:
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. Preferably the cage is near but not in the same room where frequent family activities occur. The most reliable solution is a second puppy but if that is not feasible try these other suggestions.