How do they fix a slight superior displaced medial menisucs? I have a lot of pain and clicking in the knee.

Depends on the tear. Depending on the size, and location of the tear, the meniscus can be repaired or excised. If you are having mechanical symptoms like (locking, clicking, or catching and swelling), you should have knee arthroscopy. You do not want to continue to experience these symptoms. The meniscus tear can get larger, or became unrepairable so that most if not all of the meniscus needs to be removed.
Possible arthroscopy. I am not sure what you mean by a superior displaced meniscus, but... First, you need to be evaluated by an orthopedic surgeon and have a comprehensive knee exam. Second assuming a meniscus problem is determined, an MRI may be ordered. Third assuming a meniscus tear is found, the location and size of the tear will determine the treat. This could range from conservative care to an arthroscopy.