Hey Marcin,
You should set the wyUpdateLocation property in the constructor of your form. And you should use the full path and not a relative path.
So something like this:
public Form1(){ InitializeComponent();
autoUpdater.wyUpdateLocation = @"C:\Location\To\wyUpdate.exe";}
Obviously you shouldn't hardcode the path like that, but do make sure you're pointing to the correct full path. Does this make sense?