spelled, spelt

Spelled or spelled is the past tense ( yesterday, or some time ago ) of "spell", meaning to arrange the letters in the proper order to form a word, or to to express a word or words letter by letter--
You spelled that wrong. There's no apostrophe when "its" is possessive, meaning belonging to it.
He spelled every word correctly, and got an "A" on the spelling test.
Spelled may be used figuratively--
He didn't understand, so she spelled it out for him.
Spelled may also be the past tense of "spell", meaning to signify or amount to--
He knew the leak in the boat spelled disaster.
Spelled may also be the past tense of "spell", meaning to relieve from work or duty for a span of time--
The guard was getting tired, but then a fellow soldier spelled him until dawn.

Spelt or spelt means a kind of wheat, generally used as a health food--
Spelt may be hulled and boiled for porridge.
She was on a gluten-free diet, but now she eats spelt and millet.

Now that you know that, you can say--
"She wanted some spelt from the market, but she spelled it wrong, and he didn't know what to buy."

Note--"spelt" may be British English for "spelled". In America this would be archaic, affected, or just wrong, in any formal writing.