In 2016 was released new operating system macOS Sierra. Upgrade from previous version to new one is really simple, but you can have some troubles during installation, or you want to do clear installation. You have possibility to install macOS Sierra from USB drive.
First you must create installation disc.
Download system from HERE.
Download and install DiskMaker X, mount the DMG, then drag the program to your Applications folder.
Start the program and choose macOS Sierra
DiskMaker X will find your installer and confirm that it exists. If you’ve put the installer somewhere besides the Applications folder, you can direct manually to the file.
Next, choose the drive where you want to copy installation files (USB) and you will be warned that all data on the drive will be erased. Choose “erase then create the disc”
Then DiskMaker X will create boot disk. When the process is done, you will hear nice lion roar and confirmation window will appear
Done, you installation drive is prepared for use.
Installation from USB
Restart your Mac and during starting hold the Option key. You will be asked which drive to boot from.
Select the external drive with macOS Sierra on it from the list of systems to start up your computer.