In order to do this in Yosemite, you’ll need to go back to the main screen of System Preferences and click on the
Sharing preference pane. In the sidebar, there will be an Internet Sharing option. Click on this to view its settings.
Now set the “Share your connection from” drop down to
Wi-Fi and then check the
Bluetooth PAN checkbox in the menu below. Next just make sure to check the box next Internet Sharing in the sidebar.
Once this is done your Mac should be sharing its Wi-Fi connection to devices in your Bluetooth PAN.