TK 2700 - programming it for multiple clerks

I have replaced the battery in the TK 2700.
I have performed the INIT.
Could someone tell me how to further program the machine so that I can have 4 clerks using it simultaneously, i.e Clerk1 can sign on and use the machine while Clerk2 is in the middle of logging in their transaction.
I want the 4 clerk buttons on the top row above the CASH key area.
I can assign the Clerk buttons to the keyboard but cannot get them to function as required.
I have the Programming Manual and just cannot fathom out the clerk programming.

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Thanks

Steve