To edit the whole page at once, click the "edit this page" tab at the top. To edit just one section, click the "edit" link to the right of the section heading. To edit on Wikipedia, you type in a special markup language called wikitext. See the cheat sheet for the most basic wikitext codes. See How to edit a page for more details and examples of making links, using bold and italics, linking to images, and many other things. See also Alternative method of editing.
Registered users with a little bit of editing history under their belts can move a page; this moves the page content and edit history to a new title, and creates a redirect page at the old title. This method is better than just copying and pasting the content by hand, as it preserves the article's history, as required by Wikipedia's license. Use the "Move this page" tab at the top of the article to perform a move or rename. Once you have moved a page, please click the "What links here" link in the "toolbox" in the left column and fix the links to the old page (which will be labelled as a redirect in the "What links here" list). See How to rename (move) a page for more details. Images and other media files can only be renamed by administrators and file movers. Instead, you may want to save a copy of the file to your computer, rename it there, and then upload it with the new name. Fix any links to the old file to point to the new one, then tag the old file with an "images for speedy deletion" tag: copy the template {{isd|New image name}} into the image's description page (filling in the new image name). This will add it to the Files for discussion category, and an admin will delete it for you.
First off, please don't blank articles (remove all the text from them). Such changes will most likely get reverted soon afterwards, so they are pointless, too. The procedure for deletions is explained at Wikipedia:Deletion policy. Articles that should be deleted are most commonly nominated at Wikipedia:Articles for deletion.
The easiest way to edit the redirected page is to click on the link you see at the top of the page after being redirected: "redirected from ...". For example, if you try to go to the William Jefferson Clinton page, you are redirected to the Bill Clinton page. At the very top of that page, you will see a message: "(redirected from William Jefferson Clinton)", Click on the William Jefferson Clinton link, and you will edit the redirect page. See Redirect.
Since one can link from page to page to page, how long should the ideal Wikipedia article be? A good rule of thumb would be fewer than 5000 words, unless the subject really, really needs much exposition. However, for a subject that is that complex, one can link several shorter articles together, using a hub page to tie all articles together.
For example: Foo
If you write one long article, you will need new headings anyway. If you write a long paragraph, then you need to add new linebreaks. The structure of Wikipedia is a web, instead of a text that you read linearly.
First, you need the right to publish the picture under the GNU Free Documentation License, an acceptable Creative Commons license or another free license. This means that either you created the picture and therefore own the copyright, or it is in the public domain. If you have a registered account that is four days old with at least ten edits, you can use Wikipedia:File Upload Wizard to upload the image to Wikipedia, including it in wiki pages by including its file name, the thumbnail option, and a caption: [[File:NameOfImage.png|thumb|A descriptive caption]].
