How do i cite the work for wikipedia?

There are probably many authors to the article. Go to the bottom of the wikipedia page and look at the list of references. You can probably find the original and accepted reference. Your teacher/professor will NOT be happy if you use wikipedia.org as it can be accessed by anyone making it likely to contain inaccurate facts and personal opinions.

You don't. Don't ever cite Wikipedia. As much as I love Wikipedia (and I really do) it's not a valid source for anything in school. Anyone can edit it, and put false/misleading up. Use anything from an newspaper with some authority or use a well known encyclopedia with authority (such as Britannica). And as for citation, you'll probably be using MLA format, so here's a link as to how to cite it: http://www.liu.edu/cwis/cwp/library/workshop/citmla.htm is a fairly good source. Make sure to have everything in the font Times New Roman 12pt, and have the title "Work Cited" center aligned (also 12 pt).

There is a specific wikipedia page on how to cite it as a source: http://en.wikipedia.org/wiki/Citing_Wikipedia It contains numerous warnings similar to what others have posted about whether you should use Wikipedia as a primary source.

Look for the References section at the bottom and all of Wikipedia's sources are listed there. Don't worry: Obama's article on Wikipedia is among the finest articles since it got featured on the Main Page on November 4, 2008.

There are many, many, many people who qualify as "authors" of Barack Obama's Wikipedia article. You'd spend more time listing them all than you would doing anything else! On every Wikipedia article, there is a "Cite this page" link in the "toolbox" on the left side. This takes you to a page with bibliographic details in a variety of formats. I'm including the "cite" link for the Barack Obama article as my source below.