In the dock, click the Finder icon (smiley face). Click Go (at the top), then Utilities and open Disk Utility. On the left, click on Macintosh HD (or whatever the name is of your main hard drive). The process in El Capitan is (compared with root-canal work, income taxes, or previous versions of OS X) relatively painless. How to install (or reinstall) OS X. In theory, you should have to install El Capitan only once, or never if your Mac came with El Capitan preinstalled. With the release of El Capitan, Apple took the opportunity to give Disk Utility a facelift.You can still use the software to format a startup drive—it’s similar to the steps in the previous.

I found the answer - I am sure this is the problem with all of these queries ( see my same query below).

When you get the drive it is formatted for Windows - hence Mac Journal option cant recognise it.

The actual message that Disk Utility gives is wrong - it asks you to quit and select 'Enable Journaling' but in fact that is always greyed out...

Cannot Enable Journaling For External Drive El Capitan Mac

.. Until you select 'Erase' in the options of Disk Utility bar - once you do this, it erases the Windows format from the drive ( it takes a very short time!) and then you are able to do whatever you want, select what kind of journaling and partition etc

External Drive Uses

Walmart External Drive

HTH !