First off, visit this
Link and mark down the official distances on your lawn. You can take a tape measure and pull it from your target and just look at the distances, or you can grab some marker spray paint and paint the lines. Now you'll know the minimum distances to throw 1/2 spin, 1 spin, 1 1/2 spin, etc.
After you have that marked out, it's time to develop your throw. You want to throw as comfortable as possible. For me, I throw like I throw a baseball, so there is some serious follow-through, and lots of torso movement/twist. I am also lunging forward on my left leg (throwing right-handed). The idea is to find how you like to throw comfortably without crossing the line, and if you're just starting out I doubt you'll be throwing at the line. If you throw right-handed, line the target up with your right arm, not centre of your chest. This will stop you from crossing over your chest as you throw and will train you to throw straight, thereby keeping the blade straight in the air. Once you find a comfortable throw, you can have someone spot you and see if the blade is spinning too much, or too little as it hits the target. If it spins too little, then take a half step back and throw again. If the blade is spinning too much, step a bit closer and throw again.
You want to be able to throw comfortably and just adjust your distance. You don't want to pick a distance and then keep trying to change your throw to match the distance. Once you start sticking the blades, have your spotter go grab your knives for you so you don't move from your spot. If you have to move, mark your spot with something so you know where you were.
If you marked your 1/2 spin and your 1 spin lines (probably all you need to get started) then try throwing 1/2 spin (throwing from the blade) from half way between the 1/2 spin and 1 spin line and adjust your distance from there.