Setting up a solar system is hard. There's all those physics to deal with, and the cruel coldness of space, and the occasional Vogon Constructor Fleet. But, I can help you simplify one part: scaling the original planetary distances to your local spatial limits. Yes, you can fit a solar system in your bedroom — we did.
Instructions: Type in your maximum available distance. Assume the sun is at zero, and your furthest distance is the outermost object (poor little Pluto). You may want to reduce your distance slightly, depending on the size of your Pluto. Then, choose your units and click "Calculate". You'll get a chart with scaled measurements in distances from the Sun, as well as from the prior astronomical object. Then, arrange your planets accordingly. Or not. It's your solar system.
Not quite sure how big the Solar System is? Scroll through Josh Worth's site, If the Moon Were Only One Pixel, and you might be surprised.
For reference, an "AU" is an "Astronomical Unit," or the distance from the Earth to the Sun. The true distance varies over each calendar year as Earth bumbles merrily around its star, so scientists have averaged the AU to exactly 149,597,870,700 meters (roughly 150 million kilometers, or 93 million miles). Also, none of the planetary objects have perfectly circular orbits, so all the distances here are averages of their orbits. Learn more at Universe Today.