What is the proper way to use Genius? Is he a genius? Is he genius? He is ingenius?
I am not.
Welcome to the forum.
"Genius" is used as a noun in "He/she is a genius".
However, it is also used as an adjective these days: "That is a genius idea!"
"Ingenious" is an adjective too but "He is ingenious" does not mean the same as "He is a genius".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.