The easiest way to get the rubber tires around the wheels is to soften them in warm water first, this makes them quite pliable for a minute or so.
Be careful not to scold yourself in the hot water - let it cool a little first and use tweezers to remove it from the water.
These images show the method and the video at the end shows how to do it using the tires on our Shelby Mustang - the principle is the same.