Hello, Olga.
To translate interface texts go over the following steps:
1) Add the language into which you want to translate your texts to the Common/Languages branch of the configuration tree.
2) In the Edit menu, click Edit interface texts
3) Click Find, it opens the editor window.
4) Fill interface texts in your language to the corresponding column.
To see interfaces in the language you added in Designer mode, in the Configuration menu click Designer language and select the language you want.