Installing a new clutch is a maddening affair, mostly because you have to steer a massive transmission under your car. This is a must do to keep the clutch disc from slipping out of engagement with the input shaft. To save yourself some time and effort, use the clutch alignment tool kit at this point to make sure this doesn't happen.
These tools usually come with complete clutch kits, but if you're just replacing clutch plates, you probably won't. These tools are very simple and are made of injection moulded plastic or nylon and you will need the one that matches your transmission. It's a matter of knowing the number of splines on the input shaft. It will not work if the splines are not aligned. Don't try to fudge it with a tool that doesn't fully engage the spine. If your clutch alignment tool kit doesn't fit the pilot bearing/bushing, you need to find the right one.
On the back of the engine, the flywheel is bolted to the crank, and inside the crank are grooves for the bearings. The tip of the clutch alignment tool locks into the bearing, keeping the clutch in place. The clutch has two sides, one side is usually marked with the flywheel and must be installed correctly. The tool goes into the clutch disc and then installs the tool into the bearing on the flywheel. It shouldn't be moving around at all. Next, install the pressure plate and actuate the bolts. There will be a gap between the plate and the flywheel until the bolts are tightened. Each bolt must be torqued to specification using a three-step process (hand-tightening, half-torque, full-torque).
First, insert the clutch alignment tool kit into the clutch disc, making sure the clutch is facing the correct direction. The clutch alignment tool kit should go all the way through the spur on the disc, then place the clutch on the flywheel and engage the alignment tool into the guide bushing or bearing in the center of the crankshaft. Tighten the clutch onto the flywheel. Put the clutch on the flywheel, install the pressure plate to the flywheel and actuate the bolts. Swing the alignment tool to make sure it is fully engaged and seated in the guide bushing/bearing. Tighten the platen bolts in a criss-cross pattern, then to specification. The clutch alignment tool kit stays in the clutch until you are ready to install the transmission. While the pressure position should stop the clutch from moving, don't risk pulling the tool out too early. When you're ready to install the gearbox, eject the tool and slide the gearbox into place.