What is crashing: Xcode or your project?
If Xcode is crashing, start by narrowing down the problem. Can you create new projects? Can you open other projects? If you can create new projects and open other projects, you know the problem is with the one project.
If your project is crashing when you run it, create an exception breakpoint by choosing Debug > Breakpoints > Create Exception Breakpoint in Xcode. When your app crashes, the exception breakpoint will show you where in your code the app crashes. You will have to post your code for anyone to provide additional help to solve the crashing problem.