There are many different methods to refer. Some frequently used systems are Harvard style, Vancouver style, the APA style ....
Which method you use, often depends on the discipline in which you work or depends on the publication in which your work will appear. Ask your promotor wich style you should use. Whatever method you use, be always consistent.
You need citing references in text and a reference list.
In the text, you add citing references each time you use information that you found elsewhere. This can be done by means of a footnote or by indicating a citing reference in the text in parentheses (depending on the reference system you are using).
Subsequently, add at the back of your work a reference list which lists all the source references in the text with the full publication data record. Such a reference is usually arranged alphabetically by author's name, but can also be a distinction between books, articles, web pages, etc.