How can I insert new article via code

[Dead Eddie]

I'm not going to type out a whole tutorial. Check out how it's done within the CMS (by using the datamanager):

packages/vbcms/content/article.php starting around line 905.

You can't just call mysql on its own because of some of the caching done behind the scenes, and because of how vBulletin stores the articles, you need to understand how it calculates an article's position (and update a bunch of records accordingly).