How do i access the Forms mode.i need to enter 2018 extension paymentI already entered it but is not printing on line 70I have onlne software - I do not see Forms icon

Are you using the Online version?  Forms Mode is only available in the Desktop installed program.  You should be able to enter an extension payment using the step by step method.  And it is not on line 70 anymore.

If your extension payment did not automatically show up on 1040 Schedule 5 line 71 which goes to 1040 line 17, you need to enter it. So make sure it's not already there before you enter it!

You can type estimates paid in the search box at the top of your return and click Find and it will give you a link to Jump To the screen where you enter Extension Payments.

To enter the amount you paid with an extension (including state extension) go to
Federal on left (or Personal for H&B Desktop)
Deductions and Credits
Then scroll way down to Estimates and Other Taxes Paid
Other Income Taxes - Click the Start or Update button

Next page second section Payments with Extension
Either Visit All or Click Start or Update by the extension you paid