hi, well first you could post a support question on the theme page in the store, or you could send a PM to the developer
http://www.oxwall.org/user/wuzis or
I do not have this theme but i will fly blind here and just assume it is set up much like other themes.
open ow_themes/your theme name
open the folder for master pages
hopefully you will see two files.. dndindex and general
if you are familiar with html and css at all you will know what to do next.. If not then have someone else do it for you... the css is ow_logo in the base file, be sure to change both and be sure to refresh your cache via config file. If you do not know how to clear your cash via config there are posts in the forum regarding how and also in documentation.