A simile is a literary device used to compare one thing to another. Normally, a simile uses the word, "like," or "as." For example: "He ran like a barefoot boy in a prickly pear patch." "The baby was as cute as a speckled puppy." Both these sentences are similes.
"He was rich as a Wall Street CEO."
"The child's face was smooth as silk."
"Tim was funnier than a cat wearing mittens." ("than" can also be used)
"Tony was as tall as a sequoia tree."
"Santa's belly shook like a bowl full of jelly."
Just look for comparisons using "like," "as," and "than." You should have no trouble identifying similes.