Open Terminal (it is found in the same folder as the Disk Utility app).
This can be done from the Erase tab within the app make sure that there are no multiple partitions (turn to the Partition tab to verify and correct this). Now, let's move on to the actual process. (The third-party tool will work, however.) It may allow you to create a bootable OS X 10.10 Yosemite USB drive using prior iterations of the operating system, but I have not yet tested this and, therefore, there are zero guarantees that it will work. To use this tool, Apple indicates that the Mac that you use it on must be running OS X 10.10 Yosemite.
