There are several ways for a clerk to sign on and they are;
Clerk button using a clerk secret number
By default, the clerk button is already allocated to the keyboard however; you can allocate more clerk buttons to the keyboard.
Enter the clerk secret number and press the clerk button.
The clerk is now signed on and will be shown on the top of the screen as detailed in the image below.
Press the cancel button
This will display the ‘Clerk Window’. Touch the clerk icon to sign on