These videos illustrate the how to use heat and cold to install a crankshaft and bearings easily. I use the oven for heat. Others have used heat guns and torches with good results. If using a torch, do not heat the bearing directly. Intense direct heat could damage the bearing and shorten it's lifespan. You would need to heat piece of metal and then use it to apply heat to the inside of the bearing. The refrigerator, freezer, or outside temps if it's winter in many areas are common ways of cooling. I hear that freeze spray can be quite effective and fast as well.
*It has been brought to my attention that baking engine cases that have been epoxied is a bad idea. As always, use this info at your own risk.*
This video shows how to get bearings onto the crankshaft.