GPS is enabled by default on the ES400 but to initilize it you must follow these steps. Also please make sure your device has an internet connection.

1. Click Start>Settings>Connections>GPS Assist.
2. Make sure Source is set to any and update frquency is set to on demand.
3. Click Update now, in a place where you have where the device can have satellite access. Eg. up against a window
4. Once "Last Update" says Successful, then you GPS is ititialized and should begin to work.