OS X Yosemite: Connect to the Internet using Instant Hotspot
Your Mac can automatically use the personal hotspot on your iPhone or iPad to connect to the Internet when they’re within range of each other.
Use Instant Hotspot on your iPhone (with iOS 8) and iPad (cellular models with iOS 8) to provide Internet access to your Mac computers and other iOS devices (with OS X Yosemite or iOS 8) that are in range and signed into iCloud using the same Apple ID. Instant Hotspot uses your iPhone or iPad Personal Hotspot—you don’t have to enter a password or even turn on Personal Hotspot.
Make sure your iOS device and your Mac are signed into iCloud with the same Apple ID.
On your Mac, click the Wi-Fi status icon in the menu bar, then choose your iPhone or iPad.
After you connect to the iPhone or iPad Personal Hotspot, you can check the cellular signal strength and the battery status of the iPhone or iPad in the Wi-Fi status menu.
When you’re not using using the hotspot, your devices automatically disconnect to save battery life.