The first step: Download DiskMaker X
The second step: double-click Start DiskMaker X, the first interface, the software will ask what kind of system you need to create a USB disk, currently supports 10.8, 10.9 and 10.10, select Yosemite (10.10).
Step three: DiskMaker x will automatically detect Yosemite installation files, if it has been downloaded through the Mac app Store, DiskMaker X will be found in the application folder. If you are downloading through a network disk, you can manually locate the Yosemite installation files using use another copy.
Fourth step: Then, we need to choose to install U disk, DiskMaker X support u disk and other external storage, capacity of 8GB u disk is enough.
The fifth step: Then DiskMaker X will list all the drives connected to the MAC, and select the USB disk you inserted. Be careful not to choose the wrong, DiskMaker X will format the U disk.
Sixth step: After completing the selection, reconfirm the need to be formatted the U disk. Then choose Erase then create the disk, formatting and creating the installation of a U disk.
Seventh step: DiskMaker X will prompt for administrator privileges, then just enter the password.
The eighth step: The rest is long wait until the time, DiskMaker X will automatically start Yosemite install U disk creation process. The creation time is related to the speed at which the file is copied to the U disk. As long as you wait, you can see DiskMaker X will appear after the window and automatically copy the file.
After that, DiskMaker X will pop-up prompts, then we can restart the MAC and hold down the option button, and select just finished Yosemite install U disk.