Const olFolderInbox As Integer = 6
'~~> Path for the attachment
Const AttachmentPath As String = "C:"

Sub DownloadAttachmentFirstUnreadEmail()
    Dim oOlAp As Object, oOlns As Object, oOlInb As Object
    Dim oOlItm As Object, oOlAtch As Object

    '~~> New File Name for the attachment
    Dim NewFileName As String
    NewFileName = AttachmentPath & Format(Date, "DD-MM-YYYY") & "-"

    '~~> Get Outlook instance
    Set oOlAp = GetObject(, "Outlook.application")
    Set oOlns = oOlAp.GetNamespace("MAPI")
    Set oOlInb = oOlns.GetDefaultFolder(olFolderInbox)

    '~~> Check if there are any actual unread emails
    If oOlInb.Items.Restrict("[UnRead] = True").Count = 0 Then
        MsgBox "NO Unread Email In Inbox"
        Exit Sub
    End If

    '~~> Extract the attachment from the 1st unread email
    For Each oOlItm In oOlInb.Items.Restrict("[UnRead] = True")
        '~~> Check if the email actually has an attachment
        If oOlItm.Attachments.Count <> 0 Then
            For Each oOlAtch In oOlItm.Attachments
                '~~> Download the attachment
                oOlAtch.SaveAsFile NewFileName & oOlAtch.Filename
                Exit For
            Next
        Else
            MsgBox "The First item doesn't have an attachment"
        End If
        Exit For
    Next
 End Sub

Option Explicit
Public Sub Example()
   '// Declare your Variables
    Dim olNs As Outlook.NameSpace
    Dim Inbox As Outlook.MAPIFolder
    Dim Items As Outlook.Items
    Dim Item As Outlook.MailItem
    Dim Atmt As Attachment
    Dim Filter As String
    Dim FilePath As String
    Dim AtmtName As String
    Dim i As Long

   '// Set Inbox Reference
    Set olNs = Application.GetNamespace("MAPI")
    Set Inbox = olNs.GetDefaultFolder(olFolderInbox)

    FilePath = "C:Temp"
    Filter = "[attachment] = True And [Unread] = True"

    Set Items = Inbox.Items.Restrict(Filter)

   '// Loop through backwards
    For i = Items.Count To 1 Step -1
        Set Item = Items(i)

        DoEvents

        If Item.Class = olMail Then
            Debug.Print Item.Subject ' Immediate Window

            For Each Atmt In Item.Attachments
                AtmtName = FilePath & Atmt.FileName
                Atmt.SaveAsFile AtmtName
            Next
        End If
    Next

    Set Inbox = Nothing
    Set Items = Nothing
    Set Item = Nothing
    Set Atmt = Nothing
    Set olNs = Nothing
End Sub