translating portal:lrc translatewiki.net page to luri lrc
I notice that there are still some 140 messages left to translate in the Mediawiki 500 most used messages group. I recommend that you continue to translate these as a priority, because once these are translated a MessagesLrc.php file will be created for lrc on Mediawiki and the lrc messages will be exported to MediaWiki.
To answer your question, if you want to translate a particular string, such as 'preferences', then follow the FAQ guidance to find the 'message key' (its name). You should find that the message key for the link 'preferences' at the top of the page is 'mypreferences'. Then type MediaWiki:Mypreferences/lrc in the search box at the top of most pages. Click on the 'search' icon (the magnifying glass) and you will go to the message page in lrc (which will probably be blank). Click on the 'edit' tab and you should go into the translation editor (probably the old version of the translation editor) where you can translate it.
Please let me know if this explanation is not good. I will try to improve the explanation until it is good enough to go into the documentation.