The Text tool does not support the use of Cyrilic characters. One way that you could work with Cyrillic would be to use a program like Adobe Illustrator to create the characters and import the AI PDF into Strata 3D, and then extrude them. This is actually how most users prefer to create text and logo designs.
In order to use non-English characters in the Text tool in Design 3D CX 7, you must first install the needed fonts for a particular language onto your computer. This will make them available for the Text tool.
Every language has its own fonts to handle special characters such as umlauts and many others. Some fonts can be downloaded free from the internet.