You should train someone when they start a new job.
Adam hires Fred at a data entry center and is responsible for his success.
Adam wants Fred to become productive.
Adam spends a week working with Fred on how to use the system and enter data.
Adam immediately sends Fred to work and puts him near someone, so he can ask questions.
Fred learns to navigate the system and gives good results after the week's training.
Fred has a rough time learning the system and messes up a lot of the data entry jobs until he learns it.