"In-text citation" means that you refer to (or cite) the ideas or words of another as soon as you write about them in your paper. There are several ways to do this: using quotation marks for exact words, summarizing or condensing without changing the meaning, and paraphrasing or using your own words.
Here are specific examples of ways to handle in-text citation in APA format.
APA In-Text Citation Basics (Purdue OWL)
APA In-Text Citations Specific Examples (Purdue OWL)
Conducting Research Literature Reviews by 
The Literature Review: A Step-by-Step Guide for Students by 
Succeeding with Your Literature Review: A Handbook for Students by 
How to Write Your First Thesis by 
A Practical Guide to Dissertation and Thesis Writing by 
Thesis Writing for Master's and Ph. D. Program by 
Writing a Graduate Thesis or Dissertation by Literature Review How To (CSUN University Library) offers useful tips on how to write a literature review and provides you with information on things you should and should not do.
Literature Review (Purdue OWL)
Review of Literature (University of Wisconsin)
Write a Literature Review (UC Santa Cruz)
