Q: How do I work the personal hotspot that is new with this software?

You may need to reply with more information about what it is that you are wanting to do.

Two possibilities that I can think of:

1. You want to connect to the internet using iPhone cellular data and then connect your MacBook via USB, Bluetooth, or Wi-Fi to get to the internet using your phone's cellular data: Share your Internet connection with Personal Hotspot - Apple Support

2. Your MacBook is connected to the internet via an ethernet cable (requires an adapter to do that) and you want it to share that connection via wi-fi to other devices.  More information: http://www.howtogeek.com/214053/how-to-turn-your-mac-into-a-wi-fi-hotspot/