Information you enter into the Secure Field is encrypted in your computer before being sent to teamfocus. When the data comes back, it’s decoded by your computer to display again.
In order to do the encrypting, you need a key, which your computer creates and stores locally.

To allow others to see these Secure tasks (or for you to see the Secure tasks on other computers e.g. your home computer) you need to copy that key to the other computer.