It downloads from the Inbox as your original -
For Each oItem In CreateObject("Outlook.Application").GetNamespace("MAPI").getdefaultfolder(6).Items
If you want it to also download from your sent items folder you will need another loop to process that folder e.g.

Sub AttDownload()

Dim olApp As Object
Dim oItem As Object
Dim oAtt As Object
Dim sName As String
Dim sExt As String
Dim sPath As String
Dim sFolderName As String, sFolderPath As String


    sFolderPath = Environ("USERPROFILE") & "\Desktop\KRA SUmmary\"
    sFolderName = Format(DateAdd("M", -1, Now), "mmmm yyyy") & "\"
    sPath = sFolderPath & sFolderName
    CreateFolders sPath
    Set olApp = CreateObject("Outlook.Application")
    With olApp
        For Each oItem In .GetNamespace("MAPI").GetDefaultFolder(6).Items    'Default Inbox
            If TypeName(oItem) = "MailItem" Then
                If Format(oItem.ReceivedTime, "mmmm yyyy") = Format(Date, "mmmm yyyy") Then
                    For Each oAtt In oItem.Attachments
                        If LCase(oAtt.FileName) Like "*kra*" Then
                            sName = oAtt.FileName
                            sExt = Right(sName, Len(sName) - InStrRev(sName, Chr(46)))
                            sName = FileNameUnique(sPath, sName, sExt)
                            oAtt.SaveAsFile sPath & sName
                        End If
                    Next oAtt
                End If
            End If
            DoEvents
        Next oItem

        For Each oItem In .GetNamespace("MAPI").GetDefaultFolder(5).Items    'Default Sent Items
            If TypeName(oItem) = "MailItem" Then
                If Format(oItem.SentOn, "mmmm yyyy") = Format(Date, "mmmm yyyy") Then
                    For Each oAtt In oItem.Attachments
                        If LCase(oAtt.FileName) Like "*kra*" Then
                            sName = oAtt.FileName
                            sExt = Right(sName, Len(sName) - InStrRev(sName, Chr(46)))
                            sName = FileNameUnique(sPath, sName, sExt)
                            oAtt.SaveAsFile sPath & sName
                        End If
                    Next oAtt
                End If
            End If
            DoEvents
        Next oItem
    End With
    Set olApp = Nothing
    Set oAtt = Nothing
    Set oItem = Nothing
End Sub