[Koha] About word-phrase-utf.chr file

I'm trying to search for my language, using English alphabet. For example, when i type "a", Koha can search for "â, ă, á, ạ, ả".... (these are some alphabet in my language) I'm now watching this file: /etc/koha/zebradb/etc/word-phrase-utf.chr I tried to edit this file, add some word to  map "some alphabet in my language"  "some english alphabet" but it didn't work. Am i doing right thing? And can someone show me how to edit this file? I'm using Ubuntu 12.04. Thanks so much!