Create your own subtheme in Drupal 7

Omega 5.x comes with two starterkits: Omega Default, which comes with a large set of customizable regions, and Omega Clean, which is the simpler starterkit and offers a more limited set of default regions. To use either copy it from the Omega directory to your base themes directory. For example from sites/all on the command line when starting from Omega Default:

cp -a themes/omega/starterkits/omega_default/ themes/your_subtheme_machine_name

Note that a subtheme machine name is a name that is readable by Drupal, so it should be a unique alphanumeric value that doesn't change. You can give it a human readable name (can include spaces and other characters) later.

Now you need to edit the .info file, first by renaming to your subtheme machine name. From example on the command line from your new subtheme's directory when using Omega Default:

mv omega_default.info your_subtheme_machine_name.info

Now you want to edit your info file. The only part you are required to change is the "name" section which is on the first line, this is where you give it a human readable name like this:
name = My Omega Subtheme