There is no general answer to this question as UXD has such a big variety and is required in that many fields that there is different software required for all those fields.
The first step that needs to be made is working on some analysis and collection contents and ideas for the project.go to the tools
When all contents and information has been gathered the prototyping phase can begin. There are multiple different tools available to get discovered.find out more
Once the concept was created. There are multiple new companies that provide software for UI-Design but also some classic programs like the Adobe Creative Suite.go to the tools
As an UX-Designer you should be able to work on 3D-Models and print them as prototypes in a 3D-printer to test ergonomics and the position of buttons etc.discover more
Based on the solution you concepted you might need different software to run your solution.find out more