Mandatory field settings for master data

I'm relatively new to M3 Lawson and currently working for a client that uses M3 as their primary ERP system. We have designed an Internal Control framework that contains many controls that depend on the Lawson system. One of which is Mandatory settings of fields in the customer/vendor master data. What i would like to check is how i can set/change which fields are mandatory while creating a new customer/vendor? What function do i use to set this up?