To help you focus your PICO search on qualitative or quantitative articles, you have a few options.
Option 1: Simply add the terms qualitative or quantitative to your search. The example below shows a search for qualitative studies.
By opening up the first result in my search list, I can read the details around this article and it shows me it is in fact a qualitative study.
Option 2: Try using some of the publication type filters that CINAHL provides. For example, there here is a filter that allows you to limit your search to research articles, to ensure you are finding research, and not letters to the editor and other types of articles that appear in journals.