2nd, carve the bodies up into steaks and freeze them.
3rd, pile the inedible remnants into a x4-bagged Hefty sack, and just dump it into an open garbage container elsewhere in the city. Try to choose one that has bags that look like yours already in it.
4th, clean up the mess you made. Get rid of the bedding, and perhaps the bed. Even a drop of blood left over can condemn you. Buy a new bed if necessary; in fact, plan on it. Move any bedding in and out at night, without lighting to betray you, where neighbors won't see you.
5th, clean the shotgun with extreme thoroughness.
6th, maintain innocence and ignorance no matter what anyone says to you. Practice lying and pleading in front of the mirror until you essentially convince yourself. Also practice your alibi, which is essentially a story where you came home and found that they left you a note (which you will create and print yourself) that they'll be away for a few days and that you can use the house and car, etc.
7th, get ready to hear a lot of accusations. Remember, you have no idea what happened to them. Remember what you practiced in front of the mirror. Remember, you're an ignorant innocent who has no idea what the detective is talking about. Where's your mom and dad? YOU MISS THEM. Where did they go? YOU DON'T KNOW.
8th, enjoy your nightly steak. Mmm-mmmmh! Mom and dad are being VERY good to you now!