Hi,
First you can make one new Process order settlement profile with using OKO7 t.code,In settlement profile, you can select " Variances to Costing - based PA check box . After that you can assign the settlement profile to your process order type.
Also you can make one new variance PA transfer structure in KEI1 or KEI2.
If you do the above settings, At the time of process order settlement, you will get the variance profitability document.Based on the profitability document, process order variance will flow to co-pa.
I hope this helps you and let me know if you have any queries.
Regards,
Puri.