There are various methods you can use to search for literature. It is important that you include a systematic search, so that you do not overlook any literature. The other two methods can help you get started with your search. Often, a combination of systematic searching and citation or snowball searching works best.
You search on the basis of (combined) search terms in search engines which make literature in a certain discipline (or all disciplines) searchable (regardless of availability) with the intention of finding as much literature as possible on that subject. You may expand (adding search terms you have found) or limit (cancelling search terms or filter on year of publication). You can use several search techniques in the systematic method.
You search on the basis of a suitable publication you have found earlier. For example other publications by the same author, or you go searching for other sources in the reading list of a relevant publication (authors make use of the work of others as a source for their own work, these sources will be mentioned in the reading list of the new publication). This way of searching for references goes back in time to older publications.
See if the article you found has been cited, and if so, have a look at this new article. If this article is also relevant you can see if this article has also been cited, and so on. Use a citation database, like Web of Science, Scopus or search Google Scholar. This search method goes forward in time to newer articles. Please take into account that a recent article may have no citations yet or only just a few.