The labels and messages for the static text are stored in the database in the resource table XAppResources and can be easily changed there. The Module Manager module gives the administrator the possibility to edit existing labels and messages or add new labels and messages.
If you are creating a new view or if there is a new label you want to be translated when switching the language then you just have to add "{Translate MyNewField}" in the XAML view assuming MyNewField is the name of your field. E.g. … Content="{Translate fiAccountNoL}" To use the translator for a message P2Translator.GetResource("fiAccountNotSaved") should be used in the code.
Then you have to add one row for each language for this field to the XAppResources table.
If you want to use the multilingual functionalities for a message, just use P2Translator.GetResource("MyNewMessage") and add one row for each language for MyNewMessage to the XAppResources table.