The actual adjustment amount gets reported on the Form the original amounts would have been reported on (Sch C, Sch E, Sch F....). 

If it's an additional deduction, I put it as an 'other expense' and label it as F 3115 (481a?) adjustment. 

If it's an income item (tho I've never had one of those) - same procedure.  An income adjustment can be spread over several ( 4 - ?) years, I believe.