predicting price

Hello 
i need to predict or basically forecast the average monthly price of a product for which i have 3 years of average monthly price of the product, well i thought that i could use the windowing forecasting method for it, However i am not sure how to go about it well ofcourse i have used the read excel, and and set role operator but after that i think i need to use the windowing operator but should i use split data operator before it?
can someone please ith this.