I amended my tax return 2018, I can't find the way to print it to sent it back through mail, or I need to cancel it and re-do it again, and then printed it. Thanks.

From the print center on the program, choose what you wish to print and save it as a pdf to your computer.  Go to that downloaded pdf on you computer and print using your computer prompts.  You not only have printed your return, but you have a copy on your computer for further reference.