Regardless if you are using the the Library's General Search option in the main webpage or the many Databases by subjects that we own, using the right keyword is the key for getting good results. Here are some tips for searching "Asian Americans":
Using keywords such as "Asian", "Asian American" or "South Asian Americans" are not enough to search your topic. You need to also be specific about which group you want to research, e.g. Chinese, Japanese, East Indians (for people from India--not be confused with Native American which are still described as "Indians" in many catalogs and databases), Korean, Vietnamese, Nepalese, etc. Other terms that you can used for historical research are Coolies or Indentured Labor + [Asian Group], e.g. Chinese Coolies
In the case of Japanese people, you can also identify which generation you want to work with and try the following terms to search for them: Issei (original from Japan), Nisei (second generation), Nikkei (Japanese Diaspora), etc.
Use geographical locations to narrow down results, e.g. Chinese + California; Japanese + "San Francisco"; "East Indian American" + Maryland
Find other terms from the readings provide by your professor for other terminology and try different synonyms to make sure you are finding all possible sources.
Great newspapers database to search the historical presence of different Asian groups in the United States e.g. Japanese, Chinese, etc. Do some background research to find out terms used to describe these groups in the 19th and early 20th century which may differs on how they are described today.