Hi, and thank you for your interest!
mysms is being translated using Weblate, a web tool designed to ease translating for both developers and translators.
Translation project for mysms into Serbian (cyrillic) currently contains 2754 strings for translation and is 100.0% complete.
If you would like to contribute to translation of mysms, you need to register on this server.
Once you have activated your account just proceed to the translation section.