Translation:I wash my clothes with soap.
The verb "arau (洗う)" means "to wash". "Sentaku suru (洗濯する)" means "to do laundry." "Arau" is a transitive verb, meaning that it can accept a direct object. It is an action that is done to something. "Sentaku suru" is an intransitive verb, meaning that it does not have a direct object. It is an action that is simply done, not done to something. You can do "wash" to clothes (fuku wo arau) but you can't do "do laundry" to clothes (fuku wo sentaku suru).