So, I'm going to go the opposite of what
@mgr22 is saying: It's all important. even anatomy. moreso physiology. knowledge of A&P is one of the building blocks to medicine. But while it is important, I wouldn't stress the anatomy part, especially after you pass the exam
it's a lot of information. much of your trauma assessments are based on anatomy. how would you know something is wrong if you don't know what it's supposed to look like?
The basis of the job isn't anatomy: it's patient assessment. Medical and trauma. at the end of the day, that's the basis for the job. You apply your interventions as a direct result of your findings based on your assessment.
Let me give you some advice: read the text book before class. read the chapter. come to class with questions. ask your instructor what they think is important. A lot of stuff will get thrown at you... and (speaking from experience) some stuff is covered just because it might be on the test, and has no practical value in the field. And a lot of it will be new to you, and it's very easy to start feeling overwhelmed.
EMT class (in general) isn't that hard. the curriculum is written at a 10th grade level. That isn't to say it's an easy A; people fail all the time. read the material. ask questions. form study groups. use additional resources if you are unclear on something. read the material before class. budget 8 hours a week to studying and preparing for class (in addition to going to class 2 nights a week). It can be done; after all, plenty of people had done it.