<apex:form id="frm">
        <font color="red"><apex:pageMessages ></apex:pageMessages></font>
        <apex:sectionHeader title="Attach File to Notes & Attachments"/>
            <apex:pageblock >
                <b> 1. Select the File</b><br/>
                    Type the path of the file or click the Browse button to find the file.<br/>
                <br/><apex:inputfile value="{!myfile.body}" filename="{!myfile.Name}"/> <!-- SENDS THE ATTACHED FILE INFO TO TESTMETHOD() -->
                <p></p>
                <b> 2. Click the "Attach File" button.</b><br/>
                    ( When the upload is complete the file information will appear in Next Page )<br/>

                <br/>   <apex:actionRegion immediate="true" >
             <apex:commandbutton value="Attach File" action="{!showPopup}" id="saveButton" rerender="popup"/>
                  </apex:actionRegion>
                <br/>
                <apex:outputPanel id="popup">
                                <apex:outputPanel id="popInnerOutputPnl" styleClass="customPopup" layout="block" rendered="{!displayPopUp}">
                                     <apex:commandButton value="X" title="Close the popup" action="{!Cancel1}" styleClass="closeButton" >
                                     </apex:commandButton><br/>
                                     <table border="0">
                                     <tr><td>&nbsp;</td></tr>
                                        <tr>
                                            <td align="center">
                                                 Additional Notification Recipients(Separate Email Addresses With A Comma)
                                            </td>
                                            <td>

                                            </td>
                                        </tr><tr><td>&nbsp;</td></tr>

                                     </table>
                                     <table align="center"><tr> <td>&nbsp; </td></tr>
                                        <tr>
                                            <td align="center">
                                                <apex:commandButton id="btnCenter" value="Save & Send" action="{!testingMethod}"> <!-- CALLING THE LOGIC TO CREATE AND ATTACH -->
                                                </apex:commandButton>

                                            </td>
                                        </tr>
                                    </table>
                                </apex:outputPanel>
                                </apex:outputPanel>
                <br/><apex:commandbutton value="Cancel" action="{!Cancel1}" onclick="return myFunction()"/>
            </apex:pageblock>
        </apex:form>

public with sharing class CustomEmailAttachmentsForCampaigns {

        public CPQ_Notes_Attachments__c cpq1{get;set;}
        @AuraEnabled
        public static Boolean displayPopup {get;set;}
        public CustomEmailAttachmentsForCampaigns() {}
        public
CustomEmailAttachmentsForCampaigns(ApexPages.StandardController controller) {

        }

        public static transient Attachment myfile;
        //public Attachment myfile;
        //Getfile Method
        public Attachment getmyfile()
        {
            myfile = new Attachment();
            return myfile;
        }

        public void showPopup(){
            displayPopup = true;
            }


         @AuraEnabled
        public static void testingMethod()
        {
               CPQ_Notes_Attachments__c cpqNotesandAttach;
               String idofSC;

               Sales_Campaign__c newRecord = new Sales_Campaign__c(Name = 'Test account', Account__c = 'Test');
               insert newRecord;
               idofSC = newRecord.id;
               System.debug('TESTING SC ID' + idofSC);
               cpqNotesandAttach.Sales_Campaign__c = idofSC;


                Attachment att = new Attachment(parentId = idofSC, name=myfile.name, body = myfile.body);
                insert att;
                System.debug('TESTING ATT ID' + att.id);
        }


        public PageReference Cancel1()
        {
            displayPopup = false;
             return null;
        }


    }