Sorry--the deadline to request an extension is passed. If you live in certain disaster areas you had an automatic extension until May 1, which the IRS will recognize by your zip code when you file. But it is now too late to request a further extension. If you wanted a longer extension you had to e-file the request by April 15, or get it into the mail by midnight on May 1.
If you do not owe or are getting a refund, there is no penalty for filing after the deadline. If you owe tax due, take care of filing and paying your tax due as soon as possible.