The funds must be paid directly to the college for qualified expenses, in order to avoid taxation. And you might want to wait until the last two years of college to do so, to avoid the money being considered a gift (and impacting any other financial aid). That latter consideration will change next year, under the latest tax bill.
Talk to the 529 plan custodian about distributing the money directly to the college bursar’s office. And please read the article linked below to understand how important it is to do this correctly!