Check to make sure that the bearing part of the throw-out bearing is the same, if so, use a round piece of metal that will slip inside the new bearing. Support the back of the old bearing in a vice allowing the carrier to be unsupported and between the jaws of the vice. Put the round metal piece carefully on the carrier that is sticking up through the old bearing and hit it with a hammer. You won't need to use much force as they are only a slight interference fit.
To fit the new bearing carefully place the carrier into the new bearing,
make sure that you have the hardened face out, open the vice and place both into the jaws and carefully close the jaws until the bearing has seated all the way down. Sometimes the carrier protudes past the bearing, in that case you will need to place a spacer over the bearing so the bearing can be seated properly. Make sure that the bearing stays straight when closing the vice jaws, again don't use toooo much force .
You will notice that I have used the word "carefully", this method works everytime if you take care. However there were a few throw-out bearing assemblies that didn't have a removable bearing but that should be obvious when inspecting at first.
David