Thanks..Below is the complete scenario of my code.Can you please tell me where to set these parameters in below code?

I have created the object App__c. This Object has the field App_By__c as Formula     if( App_Not_Required__c,"N/A", BLANKVALUE( App_Done_By__r.Email , "TBD" )) and App_Not_Required__c as checkbox.

I am setting the checkbox value using below Helper method

public static List<App__c> getSECApp(String pDetailId) {  
            
        List<App__c> approvals = [SELECT ID, NAME, App_Date__c, App_Done_By__c, App_By__c,
                App_Role__c, App_Not_Required__c,
                SF_Record_Link__c
                FROM App__c
                WHERE Checklist_Detail__c = :pProjectDetailId AND App_Role__c != null
              ];
                
       
                for(App__c app :appr){
                if(app.App_Role__c == 'User Experience Lead')
            )
                if(app.App_Done_By__c == null)
                {
                  app.App_Not_Required__c=true;
                }
                else {
                app.App_Not_Required__c=false;
                
                }
                }
                return appr;
   }

   public static boolean hasAppChanged(App__c pOld, App__c pNew) {  
        if(pOld.App_Done_By__c != pNew.App_Done_By__c ||
           pOld.App_Not_Required__c != pNew.App_Not_Required__c ||
             pOld.I_Approve__c != pNew.I_Approve__c ||
          
            return true;
         }  
       
        return false;
    }

Now I am opening the new page and my checkbox and other fields are getting loaded properly.

and i add save button on my page. I am calling{!saveApp} method after click on save button but checkbox value is nt getting save and it is displaying TBD instead of N/A.

public PageReference saveApp() {
        executesaveApp();
        PageReference returnPage = new ApexPages.StandardController(Detail).view();
        returnPage.setRedirect(true);
        return returnPage;
    }
    public void executesaveApp() {
        String msg = '' ;

        List<App__c> toBeUpdated = new List<App__c>();
        List<App__c> dbAppr = Helper.getSECApp(Detail.Id);

        for(App__c newA: appr){
                for(App__c oldA: dbAppr){
                        if(newA.Id == oldA.Id){
                                if(oldA.I_Approve__c == false && newA.I_Approve__c == true){
                                   newA.App_Date__c = date.today();
                                }  
                                boolean hasChanged = Helper.hasAppChanged(oldA, newA);
                                if(hasChanged){
                                        NewA.SF_Record_Link__c = URL.getSalesforceBaseUrl().toExternalForm() + '/' + NewA.id;
                                        toBeUpdated.add(newA);
                                }
                        }
           }
        }
        if(toBeUpdated.size() > 0){
                update toBeUpdated;
        }
        msg = 'Save Completed';
        
        ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.CONFIRM,
                                             msg);
        ApexPages.addMessage(myMsg);
                
        return;

    }