In your text you cite by naming author(s) and year of publication and in some cases also the number of the page where you have found the information.
When you quote, you always mention the page. When you paraphrase (use your own words to convey the information), you preferably also include the page number if you base your text on a specific passage of your source.
You can best cite your sources in the following way:
Mention the source immediately as you start using information from this source. Do not wait until the end of a paragraph. By building your text in a careful way, you can keep the source clear without having to repeat it constantly. An example:
"Smith and Jones (2010) conducted an experiment on . . . They used the following methods . . . The most important results of this research are . . ."
In this way you adhere to the principle that the source must be clear. And you do this in such a way that the text remains easily readable without an abundance of citations.