Using npp at end of test deca cycle

Hi guys i am currently doing a test deca cycle original plan was 12 weeks test and 10 weeks deca may extend to 14 and 12 though and was plannin to run test prop up to 3 days before pct,my question is how can i use npp to end my cycle so that am using deca for a longer period of time,thanks

Using npp at end of test deca cycle