So the issue your having is probably a corrupt install. Try installing the OS from a usb stick and install it to the ssd in the optical drive enclosure. [http://www.macworld.com/article/2981585/operating-systems/how-to-make-a-bootable-os-x-10-11-el-capitan-installer-drive.html] That will show you the proper way to make a Bootable USB. After youve done that, use it to install EL Cap on the ODD enclousure.