You don’t really need a special program to edit lines - just head on over to https://github.com/Treeofsavior/EnglishTranslation and make an account. Read through stuff and fix any typos or grammar issues you might spot. The new rule in place is to mark lines that you edit with an “x” at the beginning, or mark those you deem correct for release (ETC12341234->xETC12341234). That being said, lines already marked with x shouldn’t require anymore work, but it doesn’t hurt to check.
In terms of translating lines that have yet to be touched, use Google Translate. It’s best to go through both routes of translating, of which are running the text through Korean->Japanese->English translations, as well as straight up Korean->English. Sometimes the translation is more clear in one path than the other, and sometimes having both translations is useful to understand the full meaning.
There are several tips on the github page, but I strongly recommend the dual path method of translating if you’re converting lines from Korean.