"I am a person."
Translation:Mi estas homo.
Both "Mi estas homo" and "Mi estas persono" are correct and can be translated the same (although homo is directly translated to human and persono is translated to person i think). Not sure about ulo as I haven't run across that yet (although from a quick read it looks like it has masculine connotations, without necessarily being firmly a man).
When you verb adjectives, you get "to be adjective". But when you verb nouns, you get "to use noun". Think of "hammer" in English. When you hammer, you aren't saying that you are a hammer, you're using a hammer to pound something. So it doesn't really work semantically with all nouns the way verbing adjectives works with all adjectives.
In general, however, verbs work like this:
Infinitive ends with -i
Past tense ends with -is
Present tense ends with -as
Future tense ends with -os
So "Mi homos" would be something like "I will person."