Okay, @Anita, i believe you are talking about Symmetry tool. If you are using the last release you don’t have it. This tool is part of new future release 0.5.0. Right now you can try install and use test build we provide.
Please, go to website http://valentina-project.org/ and click on button Download. This will give you many options. Some of them are test builds. Find appropriate for your system (i.e. Windows or MAC OS). Before installing a test build deinstall a current version.