Translation

Hi,
I have read all the documentation but I just don´t get it how to translate certain phrases like “More subscribe options” in the widget etc.
I cannot find these phrases in the po file (it seems there is only backend text at all?)
In the forum I have read about putting constants in the wp config file – but except that it doesn´t work – it seems very unprofessional to me 🙁
The thread was from 2009, so maybe there is some hope?
Thanks!