Morality and the Good Life is a textbook that introduces philosophy through a series of excerpts from some of the best known philosophical works in the western tradition from the past 2500 years. The emphasis of the text, and one assumes the course, is close reading of seminal works as an introduction to important philosophical problems.
If you are struggling to understand the excerpts, paying close attention in class and asking your instructor questions about specific passages that puzzle you will help. Another strategy is reading the complete works rather than just the excerpts included in the textbook, as the lack of context can be confusing. For additional contextual background, you can read the eNotes summaries of the works you are studying. Stanford Encyclopedia of Philosophy is a useful online source for history of philosophy and major philosophical concepts.
Philosophical writing tends to be dense and conceptually complex. Thus it does require careful studying. You won't be able to skim over these works while listening to TV or music and checking your phone. Instead, find a quiet area and set aside period of at least 30 minutes at a time for quiet, uninterrupted reading, looking up any words you don't know, and taking careful notes.