To edit the Submit button, go to the Form Editor of your form within the form builder and click on the Submit button area. In the left side panel of the page, you will find two sections by default:
Options: from here you can change the alignment of the button (auto, left, center, right) and add additional buttons (Reset, Print)
Submit button: from here, you can change the text that appears on the Submit button
If you want to edit the Submit button in terms of design, you can do this by accessing Design section. Under Buttons, you will find various customization options, such as changing the border, font, and color, just to name a few.