Start your translation with the graphic user interface (GUI) of KDE and, first of all, with the file kdelibs.po(t). The contents of this file is spread over most KDE applications, providing the contents of their standard menus. Continue with desktop.po which is responsible for the stuff in the K menu. Then go to the apps in kdebase and, maybe, kdeutils. You will find a thorough explanation of how to do this in the section on GUI translation. But it won't hurt to see the important steps being listed here as well:
Download kdelibs.pot, the template file for all translations of kdelibs (do this download eg using WebCVS or your brand new CVS account).
Save this file as kdelibs.po to a local directory on your computer. All translated GUI files are ending in ".po".
Start translating (taking a look at the GUI section of this HOWTO and at the work of other translators could be useful now and then, also you may consider using one of the specialized programs for this kind of work).
If you are finished with kdelibs.po, test your work with msgfmt --statistics yourkdelibs.po. (Please make this a habit for all your translations.)
Tell the i18n coordinator that you are finished. He'll make up a new directory for your language then (kde-i18n/$LANG/) which is named according to the repective ISO standards (provided, there's a standard abbreviation for your language, else we'll have to make up one ourselves). He will also create subdirectories for PO files and documentation where you can commit your translation to the KDE code via CVS).
Gather a team of co-translators (if you haven't already), distribute the tasks and start building an effective "infrastructure" for your work. First of all make up a mailing list and a website for internal use of your language team. You can get both from KDE although it will be somewhat basic stuff without any fancy features -- the listserver won't accept many commands and the website doesn't allow CGI. Anyway, if you are interested, contact the i18n coordinator or the webmaster of the i18n-server. After organizing these things, you may want to take a look now and then in the "practical hints" section of this HOWTO.
If GUI translation is well under way and everything else in your team seems pretty much organized, you should start documentation translation . You will find some basic information on the KDE web site and everything else in the ksgmltools which is part of the kdesdk package. The man in charge for that part of the KDE world is Eric Bischoff. This HOWTO only provides a short overview to let you know where the journey will be going.