What kind of code do I need to have user be allowed to seach my website for information? Also, is this information based on the information in the <meta> tags, or is it defined by some other measures? Any information would be greatly appreciated. Thanks!

This code will put a search box to alternate between Google and your website:

<form method="get" action="http://www.google.com/search">

<input type="text"   name="q" size="31"
 maxlength="255" value="" />
<input type="submit" value="Google Search" />
<input type="radio"  name="sitesearch" value="" />
 The Web
<input type="radio"  name="sitesearch"
 value="website.com" checked /> Search<br />
</form>

This code will put a search box to alternate between Google and your website:

<form method="get" action="http://www.google.com/search">

<input type="text"   name="q" size="31"
 maxlength="255" value="" />
<input type="submit" value="Google Search" />
<input type="radio"  name="sitesearch" value="" />
 The Web
<input type="radio"  name="sitesearch"
 value="website.com" checked /> Search<br />
</form>

I'm a little confused, and I'm sorry I'm new to this, but what goes in the HTML portion, and what would go in the external CSS?

You don't need to use CSS to create a search box. The code above is the HTML form.