If you are struggling in a course, you should always first contact your professor or teaching assistant to discuss expectations, go over previous exams and papers, and clarify concepts and the material. It's also a good idea to contact your advising dean, who can help you review your study habits and create a plan.
For more assistance, you can look for a tutor or visit a help room. Help rooms are sponsored by the academic departments and are staffed by graduate students. They are open at various times for students to drop by and ask questions about homework and material. There are also a variety of tutors available. Academic Success Programs offers a free group tutoring service in a variety of subjects. Here is a list of department-sponsored private tutors and help room information.