JamiLin, the suggestion from the original poster was aimed at changing the default "Hello World" post which appears after installation to help a new WordPress user figure how to do things in WordPress.
What you're asking for is a bit different (more of a "Welcome to my blog, World" message). You'll find a lot of ways to accomplish that. A good place to start is the plugin listings on the WP Codex:
Search the page for the word 'sticky'. Also, the support forums have an overabundance of info on the topic: