"I graduated" is in Past Simple tense. You use it when you mention the time. e.g. I graduated from university last year. "I have graduated" is in Present Perfect tense. You use it if you don't mention the time. e.g. I have graduated from university. "I was graduated" is correct but rather old-fashioned.

I graduated

Not familiar with the concept of being graduated (was graduated) but as with many things in English, the context would clarify which is right: - to have graduated means that your graduation took place in the past and is currently happening (as in, "I have just graduated!"). This is a form of past tense we call: present perfect. - I graduated simply means it took place in the past.

This one "I was graduated" - old fashioned, as in never heard now. (Not ever)