Yosemite should be there as a free download from App Store. In your Apple menu (the top left apple-shaped thing at every program's menu), go for Software Update.

They are incompatible at their current state for USB-booting a Mac. That's my experience of getting new ones. So, if you just bought an USB-stick, the chances are, that it is MBR-partitioned FAT32. Note: You should not use a version of Mac OS X that is earlier ('older') than the version your Mac shipped with. Contains an installation of Mac OS X 10.4.5 or later, or Mac OS X 10.5 or later, which is compatible with (or shipped with) the Mac that the USB device is connected to.Has been formatted with a GUID partition type.Intel-based Macs support starting from an external USB storage device's volume that: The knowledge base article HT1948 states: Starting from an external USB storage device (Intel-based Macs).Disk Management From the Command-Line, Part 2.DISKUTIL(8) - BSD System Manager's Manual.How to Burn OS X Yosemite to a USB Flash Drive.So, let's figure out something smarter on that.

Anyway, I absolutely, positively don't want to do that on all of my Macs. Argh, argh! When I resumed, it picked a better server and I got rest of the file in 10 minutes or so. It downloaded a hour or so and choked completely. When I downloaded mine, it said 6 hours of load time. The amount of downloading needed is easily 5+ GiB. Funny thing, the operating system 10 has a version 10 released. Latest OS X version Yosemite or 10 is out.

Upgrade mac os