A database is a collection of many different academic journals that can all be searched at once. Most academic journals use a peer-review process to review articles for quality before publication.
You search a database by creating a search query. Search queries use search terms and can have Boolean Operators and punctuation. Based off your search query, you will get a list of articles (and other resources) as results.
Turn your research question into search terms.
Look at that article's keywords. Keywords are usually written underneath the article's listing in your search results.
Different databases use different keywords. By reusing the keywords, you are learning to speak that database's "language".
Some databases will give you suggestions for search terms when you start typing in a search box. These are terms that the database absolutely recognizes.
Sometimes, the suggestions will be several terms in the same text box, all separated by the Boolean Operator or. This means that the search engine will search for all those terms at once.
Always check before you select a string of terms. Some of the terms might not be equivalent for your specific research topic!
You can build a research topic through a mind map. You can use pieces or paper or textboxes to arrange your ideas.
In free association, you allow your thoughts to flow freely without interruption. You later review your thoughts and select what is useful/interesting.