Before install OS X 10.10 Yosemite on Acer Aspire One, you need to setup a bootable installer usb drive. you need a computer running Mac OS X Snow Leopard (Mac OS X 10.6.8 ) or later, as you need access to the Mac App Store to download Yosemite before creating the installation drive. If you don’t have a computer with Mac OSX system, you can borrow one for a while.
STEP 1: Log in Mac App Store and download OS X Yosemite (OS X 10.10) .
Step 2:Insert the USB drive (8GB or more). Usb 3.0 flash drive
Step 3:Open /Applications/Utilities/Disk Utility, highlight the USB drive in left column
Step 4: Click on the Partition tab, Click Current and choose 1 Partition.
Step 5: Click Options, then choose Master Boot Record.
Step 6: Under Name: type USB (You can rename it later. Acer Aspire One)
Under Format: choose Mac OS Extended (Journaled)
Click Apply then Partition.
Step 7: Download UniBeast and run it, Click Continue, Continue, Continue, Agree.
Step 8: At Destination Select, choose USB and click Continue.
Step 9: Choose Yosemite on the Select OS Installation screen, Click Continue.