To find relevant articles you will need a good understanding of your topic. The first step in searching for articles on any database is to analyse your topic.

A sample topic might be:

Asthma is a reversible obstructive lung disease, caused by an increased reaction of the airways to various stimuli. It is the leading serious chronic illness among children. Asthma can be triggered by allergies among other things. Identify some common factors that may cause allergic reactions, resulting in asthma attacks in children.

Subject dictionaries or encyclopaedias can be used to clarify terminology.

For this sample topic, you should have a broad understanding of asthma, allergens, and allergic reactions.