If you are new to writing for publication, here are a few sources that can help get you started.
Story, Not Study: 30 Brief Lessons to Inspire Health Researchers as Writers by 
The Craft of Research, 4th ed. [print] by 
How to Write a Lot, 2nd ed. [print] by 
Essentials of Writing Biomedical Research Papers, 2nd ed. by The journal where you are submitting your abstract may have rules for the type of abstract they accept (structured vs. unstructured). Be sure to check the author guidelines for details.
The purpose of the background or introduction is to introduce your topic, identify the problem being studied, and establish your research objectives. It also should logically lead to the next section of the paper, your literature review, by setting up the subjects that are relevant to your topic.
The literature review is the section where you highlight the most relevant sources for your topic. It is the section where you define the scope of your topic and establish why your research project is necessary by identifying a gap in the literature. In addition, depending on your topic, it may also be the section where you identify relevant theoretical frameworks and define concepts.
The methods section provides a description of how the research was done. It is the section that begins your case for internal validity and allows for reproducibility. It may or may not include references to other sources. If you use methods based on another person's work or guidelines, you'll want to cite those here. If your method is novel or unusual, you may also want to cite sources that help explain the choice.
This is the heart of your paper. It is where you report your findings without interpretation.
These sections are where you interpret the results and tell your readers why those results are significant.
