Need to add Diagnosis Code to signed visit

How do I add it with the psychiatric eval, what I call the Progress Note so I can use my own template. Do not see any place to add it after the fact. The appt had to be deleted because an old default CPT was in it and that is where the Diagnoses were with Treatment Plan. Urgently trying to move forward and wondering if this is why one of my other evals keeps getting denied for "no diagnosis codes" even though I see them entered on same date of evaluation.