Once you have created your assortment and pushed into Item Plan, your planned sales will be spread evenly among the planned weeks. To better plan a seasonality curve you must generate a sales forecast. For more information on generating a forecast, please refer to this article here.
You will want to follow the Spread Current workflow when pushing newly added products (no sales history) from AP to IP. In the forecast menu you will have two options to generate returns.
Returns will be generated based on the planned return rate from your Merchandise Plan. You will want to make sure that "return rate" is selected as your option for returns calculation.
Manual Return Rate
You will manually enter a return rate for the product forecast being generated. You will want to make sure that "manual rate" is selected as your option for returns calculation.
After you have selected your preferred method, your sales and returns will now populate based on your planned sales curves and return rates.