If you filed Form 1040 or 1040-SR electronically and it was accepted by the IRS for 2019, you can e-file Form 1040-X. You still have the option of printing and mailing your Form 1040-X if you prefer.
If your initial return was rejected and you didn't mail a return, you can Correct and Resubmit your e-file and do not need to complete an amended return.
If your amended return indicates you owe tax, you can pay that tax liability in the same way you would for your initial filing. See Tax Due Payment Methods (Federal Only) for details. The IRS doesn't support direct deposit for amended returns, so refunds will be issued by paper check.
In TaxAct, how you prepare your amended return has not changed. You can find detailed steps for amending and e-filing your federal return at Form 1040X - How to Create an Amended Return.