I don't think anyone here can help you, if you give such a vague description.
What's your OS? What version of prboom+ did you install? What installation method did you use? How did you configure it?
If you wrote or edited a configuration file, post it here. If you configured it with a GUI post some screenshots.
Then I think you might have a decent chance of getting a helpful reply.
Just to be clear: This isn't meant as some form of attack on you. If you want help, you really need to give more information.