Upgrading:
Wifi Fixer will be routinely updated.
When it is, you will be given a notification by Google Play.
The process is identical to any other app, you simply tap Update and the app will download and install.
The service will start itself back up after a while. You don't have to do anything special.
Important: If resources in an app are changed, odd behavior can result on update.
If this happens, either uninstall and reinstall the app, or reboot the device.