All you need to know for a new language is described in the manual here:
www.limesurvey.org/manual/Translating_LimeSurvey
Creating and maintaining a new language is quite a bit of work. I am not familiar with the differences between Eastern and Western Armenian to judge, but if they are minor, i highly recommend to think twice. Because even maintaining can be quite some work and a language that is at less than 50% in terms of translations doesn't help much.
Me for example, I work on the Brazilian Portuguese, and I am not the only one. But I was busy with work for the last couple of months and we are at 94%. 6% missing translations means 255 strings to be translated. So it is not just translating it once, but keeping it up to date.
Armenian for example is currently at 11% (5,223 missing translation strings). A interface translation of only 11% is not really helpful, because you will run into untranslated strings all the time anyway, so you could probably just use the English base version.
But enough pessimism. If you are really interested in having a Western Armenian translation of Limesurvey you can follow the link above where it is described on how to create a new language for Limesurvey.
Keep in mind, that most of this is for the backend (so for the survey creators) and a few strings for the frontend (which the survey takers will see).
If you have any further questions after this, let me know. I am glad to help.
And seems like I will have to work on updating PT-BR, because 94% translated is not acceptable.
