Well, it's too late for a starter now. Typically you do one 1-2 days prior to your brewday. There's some good threads here, just search for 'starters.'
You'll be fine, don't sweat it. I've been using smack packs for months w/o a starter and my beers turned out great. It's when you get into the higher OGs and bigger beers that you really should use a starter.