Omega 4: manually installing a subtheme
go the omega theme folder omega\starterkits select : default or extended folder and copy in site/all/themes . 
change folder name default or extended to your subtheme name for example "alex".

go to your theme folder finde the extended.starterkit.inc or default.starterkit.inc and change to your theme name in my case is: alex.info

open alex.info and change name and description of your subtheme.