This is the simplest possible install procedure: 1. Insert USB stick into USB drives. 2. Restart by holding the Alt key (or Option key, depending on the keyboard model). 3. Once the start options appear on the screen, you can release the ALT key, select the Install option and follow the instructions. You can choose to erase/format the hard disk before installation - recommended. Installing or upgrading your software from a USB Stick is a quick process and can take 10-15 minutes to complete. It will sometimes look as though nothing is happening but please be patient and allow the process plenty of time to finish. Step 1: Reverse any hardware upgrades and bring the machine back to its original Apple approved hardware. Step 2: Install or upgrade. Step 3: Upgrade your hardware, piece by piece as much as the system will accept. Apple makes software for hardware components with particular specs. Other components might work, but they'll never be a 100% match for the OS or any other software or even the rest of the hardware components.