About 5-7 days before the trip, Tibet (entry) permit will be issued to your Tibet tour operator. Then, your tour operator will send you the permit depending on how you enter Lhasa.
If you fly from a Chinese city (Beijing, Shanghai, Chengdu and etc), your tour operator will courier the original permit to your booked hotel in Beijing, Shanghai or Chengdu where you take flight to Lhasa. The courier takes at most 3 days; generally, you can get the permit at the reception upon check-in, so please tell your tour operator the right name and address including phone number of the hotel you book. The permit will be checked at the airport before you get your boarding pass to Lhasa. You have to give the original permit to your guide who will pick you up at the airport in Lhasa.
If you take train into Lhasa from a Chinese city, your tour operator will just send the scan copy of permit by email to you. You just need to print it out, either in color or black and white, a printout of permit is sufficient for you for a train ride to Lhasa. The printed permit will be checked before boarding, after boarding and even when get out of Lhasa train station. You have to give the printed permit to your guide who will pick you up at train station in Lhasa.
If you enter by overland or flight from Kathmandu to Tibet, your Tibet tour operator does not have to send you permit by courier or email. Your tour guide from the company will pick you up at Zhangmu border or at airport in Lhasa with the original permit. For more details, please refer to our page of Tibet permit from Nepal.