Check out an article at:
http://www.jet-jobs.com/articles/loggingpic.html

Basically, if you signed for the jet, it's PIC. If you flew but didn't sign for it, it's SIC. If you fetched the box lunches from the RACM, it doesn't count. Add up your Primary & Secondary (not Other) under the MC column on the Form-5 to get SIC.

Count all the Primary, Secondary, Other, and Instructor time under the MP/IP column since that's all the hours since your Cert that you signed for the jet. Some guys will subtract 10% of that (and add that amount back in to SIC) to account for locals flown under the supervision of an IP, buddy rides, trips with a senior AC, etc.

Whatever you do, be able to explain how you got the numbers, and be ready to input the numbers the way the app specifies.