I presume you mean to start after replacing the timing belt...as they can't start or run without it. While the actual mechanics of replacing any timing belt my seem fairly basic...just removing covers, etc., the technical aspects are very exacting. Any deviation can cause damage or at least the engine not to start. If you turn over or change any part of the engine while the belt is off, not only do you substantially complicate things, you can easily cause lots of - even destroying - engine damage, especially if it is what is known as a 'no clearance' engine. (That means there isn't enough room for the pistons to clear the valves if the pistons go up - compression or exhaust strokes - while the valves are in the down or open position). The timing belt (or chain) works to assure the Cam shaft - which controlls the valve opening and closing timing, and the main Crank shaft, which controlls the piston stroke, are positioned EXACTLY where they need to be. Every part of these items must be exactly on time so each cylinder has all valves completely closed and the piston at the top of its rotation when the distributor tells the spark to flare, likewise the intake vale open when the piston is down, allowing fuel in, etc. All these things are going to happen 1 to 6 or 7 thousand times a minute! Getting all those things at there exact locations, especially if you didn't put marks on the flywheels and engine when disassembling, are way past any possible Wiki discussion. Especially with an electronically controlled motor, a good level of mechanical engineering understanding and several fairly expensive or specific testers and equipment is generally needed. As is exactly specific setting data for the motor. Any variation will result in a motor running very badly if at all. It will start with finding TDC of cylinder 1. That is top dead center of the fisrt firing cylinder off the distributor rotation, and aligning the parts to be so the valves are closed and the pistion up (or off by an engineered amount provided). this actually happens 2x in any 4 stroke system, but one is fire the other compression stroke, meaning it's easy to be off 180 degrees if done without equipment checking or other indicators. And remember, all the while, you need to secure the valves in there up position to assure they don't get hit by the moving pistons. All that said, there is always the chance you did everything correct with your replacement, and still have something like a wire disconnected.