In certain manufacturer's panels, there is a dedicated grounding block. It won't be attached to the main neutral buss, it will just be screwed to the back of the panel. Your panel has to be bonded to use this type of grounding block. By Bonded, the factory supplied green bonding screw must be installed through the neutral buss into the back of the panel. Neutral and ground wires provide very different and distinct services. Neutral provides for continuity of electrical circuits. Ground wires provide protection, safety to the user of the circuit. They are not interchangeable, Neutral wires are insulated for a reason, anywhere that there is a live circuit and the neutral wire is disconnected, the circuit is broken. (The only exception being double or triple pole circuits. But even now most residential double pole circuits require a neural for timers, clocks or transformers for electronic equipment.) The neutral wire coming from a potential load back to the panel is just as dangerous and carries just as much load as the hot wire. An uninsulated ground wire is NOT suited for this purpose.
Ground, neutral and hot need to stay together, beginning and ending in the same place. You could seriously overload the neutral in a subpanel or it's feeder wires, by running too many neutrals into it. Neutrals are not fuse protected and the wire could see extreme heat before the breakers ever trip.
When it comes to electricity, using the go ahead anyway plan when you don't know what you're doing, can land you with a burned home or a fast trip to dead. Always ask, never assume anything will be alright when you just don't know.