Transform Your Mac OS X Yosemite into a Convenient WiFi Hotspot

Step 3: Choose Internet Sharing--->Ethernet--->Wi-Fi--->Wi-Fi Options

Step 4: Here, you set up parameters such as Wifi network name, Wifi password, then click Ok

Step 5: Click back on Internet Sharing once again, then select Start to initiate Wifi broadcasting

At that point, other devices can connect to the Internet via the Wifi network broadcasted by your Mac OS X Yosemite computer.