I'd suggest you do a little research on the "robots.txt" file. But basically, this is all you need to do, IF and only IF you don't mind the bots crawling all parts of your site. Open notepad, and paste the following into it:
User-agent: *
Disallow:
Save that as robots.txt into your ROOT web directory. What this does is this:
Whenever a bot, for example, Googlebot, crawls your site, the FIRST thing it does is look for that robots.txt file to see if your site is OK to crawl, if it is, it will crawl and index it. Simple as that.