"I get it" is present tense. "I got it" is past tense. To get can mean either "to understand" or "to pick something up (at a store)" or "to retrieve". I'm guessing you mean "to understand". So if someone asks "Do you understand what I mean?", you can answer "Yes, I get it." If someone asks "Did you understand what I said yesterday?", you can answer "Yes, I got it." In regular conversation between two people, however, you will hear both. Don't touch the candy. Ok, I get it. If you touch the candy, you're in trouble. Look, I got it! Even though this is all happening in the present, you can use "I got it" to emphasize the fact that you really understand. It's the same as saying: "You just told me not to touch the candy, ok, so I got it! Don't tell me again."

Either: I've got it or I get it Both mean the same thing