Whether you choose to quote, summarize, or paraphrase sources you use in your research paper, you must cite each one. For rules and examples in MLA 8th ed. style, look here:
If you use online citation formatters provided free on the internet or within a library database. Remember that computer generated citations are not foolproof. Be sure to review them for accuracy.
This video has good tips for Using a Citation from a Citation Generator.
If you are writing a long paper or thesis and want help organizing your sources and citations, try Zotero or EndNote, both of which the library supports.