To boot from the installer stick, hold down the Option key during Mac system start, and select it from the startup volume menu. The easiest way is to download OS X from the App Store. I’ll show you both methods in case one isn’t working for you.
INSTALL OS X EL CAPITAN DOWNLOAD ON EXTERNAL SSD INSTALL
Type you password (It would be hidden, and cursor would not move) Install OS X There are two ways you can install OS X on to your external hard disk: by reinstalling OS X from the OS X Utilities repair screen or by downloading OS X from the App Store and running the installer.
![install os x el capitan download on external ssd install os x el capitan download on external ssd](https://eladnava.com/content/images/2016/04/logo.png)
You do not need to install it, just download.
![install os x el capitan download on external ssd install os x el capitan download on external ssd](https://miapple.me/wp-content/uploads/2015/06/Installing-OS-X-10.11-El-Capitan-on-external-drive_01_disk-utility-partition.jpg)
It's very simple, you only need an Install OSX *version*.app file and a USB stick.
![install os x el capitan download on external ssd install os x el capitan download on external ssd](https://media.fonepaw.com/mac-update/download-install-macos-high-sierra.jpg)
Why can't you use a USB stick? If that's because you can't buy it from Apple Store, you could use any 8GB+ stick to install drive. No, you need disk or USB stick to install it.