Yes you can file an extension if you owe taxes. The taxes owed can be paid with the extension request. Any taxes owed have to be paid on or before April 15, 2019 to avoid a failure to pay penalty. The extension request only gives you an additional six months to file the 2018 tax return, not extra time to pay taxes owed.
Go to this TurboTax website to e-file an extension request - https://turbotax.intuit.com/irs-tax-extensions/