This operation should only be carried out by suitably trained personnel.
Carefully examine the new grindstone for any signs of damage such as chips or cracks. Also look for signs of water damage (a dark stain in one area that will leave a grindstone out of balance) If the stone is damaged or you are at all unsure, DO NOT use that grindstone. Make sure that the mounting surfaces of the grindstone are clean with no grit. The mounting faces of the stone carrier should be similarly clean. Tighten the retaining nut firmly.
ALL new grindstones should be dressed after fitting. If the grindstone runs out of balance loosen the retaining nut and rotate the grindstone on it's mounting about ¼ turn. Re-tighten the retaining nut and try again.