Q. Where should I go to find out how to write an abstract?

Most scholarly articles contain an ABSTRACT. The abstract is a brief written statement of the main point of a paper, or of the highlights of a study, that is placed at the beginning of a longer report. The abstract summarizes what the article is about for the reader.  

Students usually need to write Abstracts because they are writing a paper in APA style, and their professor requires them to include an Abstract. Because the Abstract is a brief summary of what is in your paper, it should normally be one of the last things you write.

Berkeley's Center for Academic Success (CAS) on each campus is where you can always go for help with college writing, including abstracts. But here's how an APA abstract (7th edition) should be set up: 

After the Cover sheet/Title page, begin a new page. That page should already include the page number like your other pages. On the first line of the abstract page, center and bold the word Abstract.

Beginning with the next line, write a concise summary of your paper. Do not indent. Your abstract should be a single paragraph, double-spaced, and between 150 and 250 words. For a Research Methods or Honors course the abstract may be longer, and contain items such as your paper's purpose or research topic, research questions, methods, results or data analysis, conclusions and recommendations.¹

Here's a graphic from the CAS's APA 7th Edition Workshop about Abstracts:

MLA Style Center has a page explaining writing abstracts for English, Literature, Art & Humanities classes, with an example:
https://style.mla.org/how-to-write-an-abstract/

The Purdue OWL website contains more information showing how to write abstracts for research methods, scientific or medical reports:
https://owl.purdue.edu/owl/subject_specific_writing/professional_technical_writing/
technical_reports_and_report_abstracts/index.html

¹ Purdue Online Writing Lab (n.d.). APA General Format.     https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/general_format.html