Take a look at the sentence again:
Because Simon thinks that he has big, ugly toes, he insists on wearing socks
everywhere that he goes at the beach, in the shower, or around the
house, you will find Simon with socks on
his feet.
The comma between house and you is completely correct. At the beach, in the shower, or around the house is a long string of prepositional phrases. You will find Simon with socks on his feet is a main clause. When a string of prepositional phrases introduces a main clause, you should use a comma to connect the two sentence parts.
Go back to the sentence to try again.