These require two parts;

a)

Chzz is 98 years old.<ref> "The book of Chzz", Aardvark Books, 2009. </ref>

He likes tea.<ref> [http://www.nicecupofteaandasitdown.com Tea website] </ref>

b) A section called "References" with the special code "((reflist))";

== References ==
((reflist))

(an existing article is likely to already have one of these sections)

To see the result of that, please look at user:chzz/demo/simpleref. Edit it, and check the code; perhaps make a test page of your own, such as user:Chzz/help/reftest and try it out.

Chzz was born in 1837.<ref name=MyBook>
"The book of Chzz", Aardvark Books, 2009. 
</ref> 

Chzz lives in Footown.<ref name=MyBook/>

Note that the second usage has a / (and no closing ref tag). This needs a reference section as above; please see user:chzz/demo/namedref to see the result.

You can put anything you like between <ref> and </ref>, but using citation templates makes for a neat, consistent look;

Chzz has 37 Olympic medals.<ref> ((Citation
 | last = Smith
 | first = John
 | title = Olympic medal winners of the 20th century
 | publication-date = 2001
 | publisher = [[Cambridge University Press]]
 | page = 125
 | isbn = 0-521-37169-4
))
</ref>

Please see user:chzz/demo/citeref to see the result.

For more help and tips on that subject, see user:chzz/help/refs.