Derive Revenue Account Segments based on the item category assigned at item level

Hi Team,

There is an requirement where we need to derive two segments of revenue account based on the item category assigned at item level.

I created mapping set where and added input source as Transaction item category identifier, but i am not sure where we put the input and output what should be the input in the transaction item category identifier.

If any body knows the solution please guide me.

Thank you,

Asif Sayyed