When looking for specific journal articles related to a topic such as paleoclimatology, you can browse through specific scientific journals by choosing Journals by Title in the upper-hand corner of the OneSearch.
For your class assignment, your instructor recommends browsing these journals either electronically or physically. Using these journals might be your best place to start with finding suitable articles for this assignment.
Each one of these journals will have primary research articles available that discuss paleoclimate, proxies, and the time periods required. When evaluating and choosing an article from these journals, make sure you see an option to open the full text.