Unless it is a launcher theme, then it would most likely require a custom rom, like cyanogen mod. These custom roms contain the Theme Chooser engine that will allow you to apply themes on the fly.
Now there is a mod called xposed framework, along with the xtheme engine module, that will allow you to theme your phone in a similar way that the theme chooser works. To use this method, you must be rooted and the theme would need to be ported over to work with the xtheme module. I have ported over several cyanogen mod themes to xtheme, so I could port over a theme for you once you get your phone set up.
If you are unfamiliar with the xposed framework and the xtheme engine, take a look at these threads:
xposed framework
xtheme engine
If you need to root your phone, follow this thread:
[GUIDE] Howto Root LG Optimus F3