Hello. All frontend text seen comes from a language file. The English (default) file is found in the core Joomla language directory just like all other extensions...
/language/en-GB/en-GB.com_dtregister.ini
DT Register has frontend translations for about 10 languages. Any other language on your site should have had the DT Reg translation loaded on install IF a translation exists in the package. If your language isn't there, you can take the English file and translate it.