Demand Forecasting AX 2012 R3 - how to add rows when there is no historical data

Hi,

I am looking into demand forecasting in R3.

I more or less understand the basics when there is historical data for an item. However, I don't understand how should one plan for demand when, for example, you have a new item and there is no previous demand?

We would like to plan by items, customer groups and subsequently by customers. However, the generated data for the new item doesn't have customer groups, nor customers - when I include customer groups in the pivot table I only get one row with the value "N/A". 

Is there a way to enter data by customer groups in this case?

Thanks,

Maja