Both of these stories have narrators that murder someone and bury them in a part of their house. Both of the narrators are caught by the police. Both have supernatural events occur to them (or, at least, a hallucination of their senses)--in "The Black Cat" the man thinks he sees the cat everywhere, and in "The Tell-Tale Heart" he thinks he hears the dead man's heartbeat. Both narrators have been put into confinement--one in jail, about to be executed ("The Black Cat"), and the other one is some other indeterminate form of confinement, from which he is eager to prove he is not insane. Both are written in the first-person point of view.
Differences between the two are in the narrator's intent in the murders--in "The Tell-Tale Heart" he planned his murder for a long time, stealthily waiting for the right moment, whereas the narrator in "The Black Cat" killed his moment with no forethought, but in a moment of blind rage. The narrators were found out in different ways too; in "The Tell-Tale Heart" the narrator confessed openly, when he was afraid of being found out, but in "The Black Cat," the police found out not through a confession, but through discovering the body themselves. The narrator in "The Black Cat" was an alcoholic, which led to his temper and problems, but the narrator in the other was not--he just claimed to have a "heightened sense of hearing" from a "disease." Granted, that disease could have been alcoholism, but it isn't specified. The supernatural thing that drives these men crazy in the stories is different--in one it's a cat, in the other it's a heartbeat. And, the purpose in telling their tales also differs. In "The Black Cat" the narrator says it is just his way of unburdening his soul before he dies; for "The Tell-Tale Heart" the narrator tells his story in a desperate attempt to prove that he isn't insane.
I hope that those thoughts helped a bit; good luck!