To connect ForeFlight to your Avidyne IFD540 or IFD440, you will first need to update the ForeFlight app to, at least, ForeFlight version 7.6. You can see your version number within the app under MORE > ABOUT.
Once you have confirmed your ForeFlight app is up to date, you will need to connect your iPad to your Avidyne system via Wi-Fi. To do so, open the iPad SETTINGS APP and tap on the Wi-Fi line and then connect to the Avidyne "LIO_WiFi" network inside your airplane. If you need a password for the Wi-Fi network, you will need to contact Avidyne Support for that password.