First off, you should know a little bit about qualitative vs. quantitative studies. 

Qualitative research is used to explore and understand people's beliefs, experiences, attitudes, behavior and interactions perhaps through focus groups, in-depth interviews, or observational studies. It generates non- numerical data, ex. a patient's description of their pain rather than a measure of pain. Example of study types could be: case study, cohort study, etc. 

Quantitative research generates numerical data or data that can be converted into numbers, for example clinical trials or the National Census, which counts people and households. Example of study types could be: control trial, meta-analysis, etc. 

More about study types and methodology descriptions on the Evidence-Based Practice Guide. 

Next, you need to have some sort of topic to search, even if it is vague. Let's use the example (breastfeeding)

Then log into a Libraries' database, we suggest starting with CINAHL as it focuses on nursing and allied health scholarship. 

Once logged into CINAHL, type in your topic into the first search bar. 

In the next bar, add words that describe either a qualitative study or quantitative study. For a qualitative study, I may type in descriptors like (interview OR qualitative OR cohort study). For a quantitative study, I could use (randomized control trial OR rct OR control trial OR statistics). See screenshot below for example. 

This is not a perfect way to search, but if the main purpose of your assignment is flexible enough to focus on study type alone, this approach will get you closer to relevant search results .

Additional tips can be found on the nursing subject guides.