To translate an application to another language you need a human translator, that is, a human being knowing what the application does, knowing the target language, knowing the rules of translation to the target language (*), and preferably knowing the language that the application was originally developed in.
(*) For example, Polish software always says "thou, do this!" because otherwise it would have to know who is reading the text: a man, a woman, several women, or several persons including at least one man. Your translator must follow common practice for the target language (for example, it would be wrong to re-phrase Polish to use nouns instead of verbs).
If you have a human translator, you can translate the application. First, make sure that no user-visible text is hard-coded, and no phrases are composed programmatically. Then, you just let the translator translate the resources. Resources for different languages will reside in different directories of your project. But the translator must know the context of each phrase, know what the application does before showing a message and what it will do after a menu item is chosen. If the translation is poor, a native speaker may get puzzled and will never choose the menu item that he/she is looking for.
There are companies specializing in app UI translation. They will want your money and you will not be able to evaluate the quality of their job by yourself, but probably this is the best you can do. (PS do not forget to ask them what happens if you change/add one or two messages.)
