Silk is pretty resilient - people have been washing it way before dry cleaning ever existed. Don't panic!
Of course, if you prefer, you can take it to your dry cleaners.
Best method: Hand wash in warm water & mild detergent. I used regular detergent like Arm & Hammer Sensitive Skin, you can use any kind of soap as long as it doesn't have oils in it. A little color run-off is normal. Be careful not to let your silk soak for too long.
Hang it up to dry over a towel. You can also throw it into your dryer on low heat for 15 minutes, damp dry.
Iron the silk when it's damp. Use a press cloth or clean paper towel, spray and steam away any wrinkles.