As our Citation Guide says, citing your sources is an important part of the research and writing process. You should cite your sources because:
Unless your instructor says otherwise, you will cite your sources using APA, or AMA citation styles for your PTA research. We have a guide dedicated to citing sources using both APA and MLA. If you would like information on citing using the AMA style, please take a look at this page from Purdue OWL.
Citations can be tricky, so as always, if you need help, please Ask A Librarian.