How could you use the word harrific in a sentence?
There is no such word in the English language.
You may be looking for the word "horrific" meaning "instilling horror," but used to mean frightening, hideous, or terrible.
"This was the director's horrific attempt at making a horror movie." (attributed to Roger Ebert)
"How is sentence used in a sentence?" is an excellent way to use the word sentence in a sentence. You could also try, "I used the word sentence twice in a sentence in which I asked how to use the word sentence in a sentence." You used the adverb wrong in the sentence. Correct any misspelled words in your sentence.