To update a staff members passwords, you'll need to have access to Setup> Staff Records.
Within here select the user from the drop down list of staff name and click load> Privileges and then click the 'Change' button next to Password, (highlighted below in red) this will bring up a pop up window for you to amend the password, then click update and hit save next to the staff members name.
The force password change tick box, will give the user the option to update their password privately once when they log in.
Please note a technicians password must be numeric.