Present Tense: spell / spells

How do you spell the word "school?"

You spell it "s-c-h-o-o-l."

Present Continuous Tense: (be) spelling

He's spelling the word "school."  

Past Tense: spelled

She spelled the word "camera."

Carla spelled the word "camera."

Infinitive: She knows how to spell the word "camera."

Gerund: Spelling words in English is difficult.