forecast planning function in IP

Dear All

We have a requirement like forecasting future prices for next year on monthly basis.

Data of prices for the past 3 years on monthly basis is available in the InfoCubes.

Can anyone please let me know how to use the "forecast" planning function in "Integrated Planning"

to predict the future prices with stepwise procedure or provide any document explaining similar requirement.

Any prompt help regarding this will be truly appreciated and awarded with points.

Regards

Suresh