Collins Dictionary gave the following rules that will help us learn how to use make it up and make up for.
(a) make up it to (someone) -If you say that you will make it up to someone, you are promising that you will do something good for them after they have been upset or disappointed, especially by you
*Make it up to someone is about a single person being wronged to some degree, often times to a second person’s benefit.
Ex. I must make it up to him for the awful intrusion of last night.
(b) make up for -To make up for a bad experience or the loss of something means to make the situation better or make the person involved happier.
*Make up for is about resolution of a mutual disagreement or conflict. Perhaps both parties in a dispute.
Ex. Ask for an extra compensation payment to make up for the stress you have been caused.