I'm using a template that is only partially translated due to additions of my own. However I'd like to add some strings to the .po files and translate them in different languages.
I've noticed all strings are called with
<?php _e('String',my_themename); ?>, but I'm confused on how to add the string to the existing translation files. I have not yet been able to find a good source to answer my question. Could anybody give a hint?