Custom language file for Help, Support FAQ Theme

I'm trying to change some of the lables in the Help, Support and FAQ theme. I'm thinking that it would be best to do this by using poedit to modify and create a custom language file. I believe this is what I did for another buddypress installation, a la http://codex.buddypress.org/buddypress-site-administration/customizing-labels-messages-and-urls/

So, I tried to modify the default.mo/.po file and then simply replace them in the language directory of the theme. So, as you probably guessed, this didn't work.

So I'm wondering how/where to place my custom files. Do I need to register my customizations through a function?

I should also note that I am making these changes in a child theme with the Help, Support and FAQ theme as its template/parent theme.

Thanks!
Ryan