Just cite the provided article. How to write the reaction paper:
(1) Summary of main findings(25% of paper)
(2) Critique of the article: reliability and validity (75% of paper)-Appropriate methodology? Results -> Conclusions? Sample: method, size, type
(3) Find strength and discuss at least one. Strong/methodology, interesting/unexpected research question, important/understand sample, or if there’s no strength discuss why not. 
(4) Craft a discussion question; open-ended questions