Wikipedia depends on volunteers, and reminds readers of this by calling itself the "free encyclopedia that anyone can edit", but what if you want to write an article about yourself? Well, you probably shouldn't. And if you do, be very careful.
First and foremost, the likelihood that you, the reader, qualify for a Wikipedia biography is relatively slim. Wikipedia's Notability guideline (see week 20) sets the threshold for inclusion relatively high on purpose.
A related issue: reliable sources (see: week 19) may not be available to verify (see: week 18) information that's important to you. Finally, it is by definition almost impossible to write objectively (see: week 16) about yourself.
If an article about you exists, congratulations! And good luck, because you can't really control what others do with it. A Wikipedia article may be a sign you've "arrived" but it's also a double-edged sword.