There are three main ways in which secondary source material can be integrated into an essay: summarizing, paraphrasing, and quoting.
Summarizing means explaining the central argument of a secondary source in your own words. It is generally the case that a summary cannot be attributed to a specific page number, so simply the date (in Harvard style) or the bibliographical information without a page number (in MHRA style) can be used. Summarizing can be helpful because it shows, firstly, your ability to extract the main point from a source and explain it in your own words. By boiling down the argument in such a way, you will be able consider several important sources simultaneously. In this way, it makes source material work for your argument, and frees up the time and space for you to develop your own response rather than laboriously outlining the argument of someone else. Make sure, though, that your summary takes into account the full scope of the author’s argument, otherwise you might be paraphrasing, which is dealt with in a different way and serves a different function.
Paraphrasing is a more specific form of summarizing, in that you are explaining in your own words a short passage from the source material. You might paraphrase a single sentence or perhaps a full page. Doing so allows you to integrate the source material seamlessly into your own essay, and to streamline passages that would be too long to quote directly. You must make sure that your paraphrase is substantially different to the original, because otherwise it will be considered plagiarism. The key difference between summarizing and paraphrasing is that, while a summary explains a source’s argument, a paraphrase explains a piece of evidence that the source uses to support that argument. Because the paraphrase refers to a specific portion of the text, it is required in MHRA style that you cite the page number in your footnote.
The selection of direct quotations to include in your essay is an important component of the overall effectiveness of the argument that you pose. Firstly, they give the reader a sense of the original style and tone of the source material. While, in one sense, professional academic writers often contrive to be neutral and evenhanded in argumentation, you may find that occasionally the style and tone of the writer is a significant component of their main point. If so, a direct quotation could allow you to highlight this feature. Direct quotations also prove to the reader that the text says what you claim it says. I don’t want to suggest that you must slavishly validate every point that you make about a secondary source, but direct quotations can often serve a helpful illustrative purpose when introducing them to your reader. Direct quotations also highlight an especially interesting or well-stated point in the author’s own words. Sometimes the original author simply said something better than anyone else ever could. If so, celebrate this fact—share this quotation with your reader.