The prefix "re" means "to do again", so that is a helpful hint as to the meaning of the two words.
= INCARNATION is a word that refers to someone being an exact match for a quality or trait. For example, if you said, "my brother is the incarnation of anger" or "my brother is anger incarnate" - you would be saying that your brother is so angry that he embodies the quality of "anger". The "carn" in "incarnation" refers to flesh or meat (of the human body). Thus, "incarnate" means "in the flesh".
=REINCARNATION is a word that means "to be born again (in the flesh)". It refers to being reborn, and is generally associated with the belief that, when people die, they will be born again into a new body.
I hope this was able to help! I love the English language, but I understand that it's hard to understand words without a grasp on their meaning, so I tried to provide that.