grammer

when to use io and ho and is non capisco mean the same as non ho capito

Hi MichaelS185, 

Thanks for your question!

The sentence "(io) Non capisco." (I don't understand/I am not understanding) is in the present tense. 
The sentence "(io) Non ho capito." (I didn't understand/I haven't understood) is in the past tense.

If someone speaks too fast, for instance, you could say:
"Scusami, non ho capito. Puoi ripetere?" (Literally: "Excuse me, I didn't understand. Can you repeat?")
This refers to something that has just happened (in the past), therefore you would use the past tense of the verb.

Let's pretend you are having a conversation with someone but you need to interrupt him/her as you don't know what he/she is talking about. In this case you cou could say:
"Non capisco, puoi spiegarti meglio?" (Literally: "I don't understand, can you explain yourself better?"
In this case you are referring to the present moment, hence you are using the present tense of the verb.

In lesson 5.8 you will find more information about the past tense: https://members.rocketlanguages.com/members/italian/lessons/456/4-8-past-tense

Let me know if you need more examples and I will be happy to help! :)