Part of being a scholar is learning to synthesize and comment on the ideas you interact with, and to develop your own voice and ideas. In your courses, you will be asked to utilize other scholar's published works to build your own arguments, so it's important to do it in a way that clearly differentiates your ideas from theirs (plus there's that whole Academic Honesty policy thing...). The following resources can tell you about how to avoid plagiarism and how to successfully paraphrase the sources you cite.
I found this video tutorial on plagiarism - from the University of Mississippi Libraries - funny as well as informative. I promise it's not long, and you can skip the parts about their disciplinary process!
These other universities have created textual tutorials for avoiding plagiarism:
A good (and short!) overview of paraphrasing from the University of Melbourne.
These sites give great overviews of what paraphrasing is and how to do it right!