To change a student's password, start by clicking on the 'Class' tab at the top of any Naiku screen (screenshot below). Next, select the class the the student is enrolled in.
Now, hover over the 'Actions' tab and select "View Class." This will allow you to view your class roster. On the right of the screen, select the "Edit" button for the student who forgot their password.
Under the password section, enter the student's new password under "Student's Password" and "Password Confirmation" (shown below). Finally, scroll to the bottom of the page and simply click 'Save.'