After completing your tax returns you must go through the File section of the program to either e-file or print and mail your tax returns.  In the File section on Step 2, when taxes are owed, you are given several options on how to pay the taxes owed.

See this TurboTax support FAQ for paying federal taxes owed - https://ttlc.intuit.com/community/tax-payments/help/how-can-i-pay-my-federal-taxes/01/26212