adding a deducxtion wage type in renumeration slip

Hi Sap gurus ,

I want to add a deduction wage type in the renumeration slip.

a)Please can you guide me with the steps in configuring this scenario

b) n pt51 there is a radio button for cumulation where there is bifurcation for earnings and deductions .In deductions i found that the wage types are linked to a ZRT table . What is this ZRT table.

Regards,

Waman