The first stage of the screening process is typically a title/abstract screening. Click on the review title, then click the "Show" button to get the the main screening interface.
The panel on the left of the screening page has general information about your review. Rayyan tries to make decisions on topics and and keywords to assist with inclusion/exclusion decisions. This may or may not be helpful.
The main (top center) part of the screen lists the articles you uploaded. To make a decision on a particular article select the article from the list. The panel below the list of references (bottom center) will display citation information related to that article (including the abstract if available). Use the include or exclude buttons as appropriate. If you are not sure about a particular article, use the "? Maybe" button.