After locating a source related to a research assignment, a student should first and foremost evaluate the quality and reliability of the source. This involves checking the credibility of the author, the accuracy of the information, and the relevance to the research topic. However, from the options you provided, there isn't a direct fit for the first step after locating a source.
If we work with the options you've given, using synonyms for your search terms could be seen as a way to refine or expand the search for additional sources, but it would be more relevant to the research phase rather than the immediate step after locating a source.
In summary, while evaluating the source is crucial after locating it, from your listed options, focusing on synonyms for search terms could be the most relevant next step if the student is seeking to find more information in a related context.