You can broaden your search strategy by using general databases. General databases cover a wide variety of subjects and include some literary criticism and analysis. They can also give you some background information on subjects that Le Guin explores in her works such as environmentalism or colonialism.
Research tip: You can find additional articles by "mining the sources". If there is a section or topic of the article that interests you, check the references of the articles to find more and similar information. Usually there will be a footnote attached to quotes that the article's author cited to. You can then go to the end of the the article and click on the linked work, which will then be an additional source.
For example, a search in Academic Search Complete, using the terms "Ursula Le Guin" and "The Word for World is Forrest" and "Environmentalism" yielded this (and many other) result:
Hovanec, Carol P. “Visions of Nature in The Word for World Is Forest: A Mirror of the American Consciousness.” Extrapolation (Kent State University Press), vol. 30, no. 1, Spring 1989, pp. 84–92. EBSCOhost, doi:10.3828/extr.19126.96.36.199.
It's important to note that I used keywords (I did not use a complete sentence) and I put quotation marks around all the words I wanted to keep together as a phrase. Additionally, using the word "and" ensures that every word or phrase in the search string appears in the results.
Keyword searching is generally what you use when you are first beginning a search. Try to break down your topic or research question into the overall main ideas; these main ideas become simple keywords which you may use to search a Library database. Keep a keyword list when you are researching a topic. This will help you remember the words you have already tried searching, the combinations you have used, and any new words you noticed in search results that you want to try in your searches later.
To pull up articles related to your topic for this assignment, you may try the following:
Ursula Le Guin and "The Word for World is Forest" and "_______________" (your topic here such as environmentalism, colonialism or culture clash)