After running your searches, you need to decide which results are best for your research. The process is like a funnel that only the best results can fit through. When you ran your searches, you needed to be comprehensive so as not to miss any important literature on your topic, but you’ll have far more results than will end up in your literature review. You eliminate inadequate results through three steps:
This leaves you with a much smaller pool of relevant and credible literature to include in your review. By processing your search results this way, you will also begin to shape your review because you’ll start to identify important features within each article, and you’ll start the process of synthesising the literature for impact. 
The first step of winnowing your results, after you have satisfied yourself that you have captured all relevant results through your search process, is to weed out duplicate records. Remember that reference management software can speed this—some programmes have deduplication functions, and others let you order references alphabetically and deduplicate results manually.
Once you’ve removed any duplicates, you screen all your results for relevance. Screening is done by reading the title and abstract of each record and discarding any which obviously don’t fit your research question. You can also, at this point, consider if the research was published in a trustworthy source. For example, if you know that the research is published in a predatory journal, it will be risky to include it in your review, as it won’t have been properly peer reviewed to give you the confidence that the research is sound. Learn more about predatory journals and how to identify them.
Having excluded obvious mismatches and results from obviously poor sources, you now will now have a much shorter list of results that look potentially useful for your review. Now you need to get the full text of the articles so that you can critically appraise them. You will see if the claims you read in the abstract stand up to scrutiny and make a final judgement on whether each article is relevant enough and credible enough to include in your literature review.
BEST PRACTICE RECOMMENDATION: never cite an article you haven't read in full. While abstracts are a guide to the content of studies, they can be misleading and if you cite inappropriate publications in your work it will be obvious to teachers or reviewers who are familiar with the work that you have not read the full study.