Sometimes one doesn’t have a wifi or cabled internet access (on an airport, in a hotel etc.) – Then you might want to connect your macbook via iPhone to the internet – Here is what you have to do:
- on the iPhone go to settings > general > network > (scroll down) and change Internet-Tethering to On and choose USB
- connect your iPhone to your Mac via USB cable
- the Mac should ask now, wether you wanna open the network settings > Yes you want!
- Click on the iPhone connection and click apply
From now on your Mac connects to the internet every time you connect your iPhone with a USB cable 
