There is information on importing from LJ (and other sites with the same codebase) to dreamwidth available at http://www.dreamwidth.org/support/faqbrowse?faqid=86 (http://www.dreamwidth.org/support/faqbrowse?faqid=86).

Information on how to set up automatic crossposting from dreamwidth to other supported sites (such as Livejournal) is at http://www.dreamwidth.org/support/faqbrowse?faqid=98 (http://www.dreamwidth.org/support/faqbrowse?faqid=98).