To find sources for the Advertisement Analysis, Advanced Search will be most helpful.
Searching for Advertising in All EBSCO Articles found over 1.7 million results so you need to narrow your search. However, your initial question is probably how do I do that? To begin, consider the following questions:
WHAT product or company is being advertised?
WHO or WHAT is pictured in the advertisement? What is included in the picture is significant in some way.
Based on what is pictured in the advertisement, WHAT values are being advocated?
WHAT colors are used in the advertisement?
Combine the answers to these questions with Advertising in an Advanced Search as shown below.
Note: You may find that combining too many search terms produces very few search results. Don't be afraid to swap a search term to see what happens.
Your assignment indicates using "a minimum of 3 professional or scholarly sources." So you will want to make sure your sources are professional or scholarly. The link below contains information on how to find scholarly sources.
Your next question, particularly if the article is not in full text, is "How can I get this article?" Answer: You ask!