Hi Neehal,
You do not copy data from flatfile into keyfigure directly in APO. You develop the necessary dataload process to get this data loaded into APO. For Example it can be done using BW route. If required, please consult your BW colleague.
1. Creating Datasource
2. Creating Infopackage to load data into PSA
3. Creating Infocube
4. Creating Data Transformation
5. Creating DTP to load data into Infocube
6. Creating variant for /SAPAPO/TSCUBE load data into APO Planning Area.
Hope this will help.
Thank you
Satish Waghmare