It's not too bad.
Simply create an instance of the FileSystemWatcher on a Form Load event for example:
VB Code:
Dim mywatcher As New IO.FileSystemWatcher 'Create new instance of FileSystemWatcher
mywatcher.Path = "D:\My Documents\" 'Specify Path to File or Directory. Which ever you need
mywatcher.NotifyFilter = IO.NotifyFilters.LastWrite Or IO.NotifyFilters.LastAccess Or IO.NotifyFilters.FileName
AddHandler mywatcher.Changed, AddressOf OnChanged
AddHandler mywatcher.Created, AddressOf OnChanged 'Add handlers to catch certain events of certain types
AddHandler mywatcher.Deleted, AddressOf OnChanged 'Use intellisense to see what others are open to you
mywatcher.EnableRaisingEvents = True 'Start the process
This is the code operates/fires when an event is detected. You would probably place your code that you want to fire when a file changes.
VB Code:
Private Shared Sub OnChanged(ByVal source As Object, ByVal e As IO.FileSystemEventArgs)
' Specify what is done when a file is changed, created, or deleted.
'This is the event that detects a file change.
'Put your code in here
MessageBox.Show("File: " & e.FullPath & " " & e.ChangeType)
End Sub