@Anonymous
You're having a rough go at it my friend. I am sorry that it is this complicated. Usually, you had the right approach, doing a customize form in SharePoint will give you everything you need...ready to go...make pretty and then publish.
But here's the thing - something must have been changed. That is not a normal "customize forms" look. Normally the screen is much thinner and there is no coloring or added button as seen in the image.
SO, if you only clicked on Customize Forms in PowerApps and saw that and did nothing else, then someone else has made this before you.
If you want to start from scratch, then go to your List settings in the SharePoint list, then click on Form Settings. Set the option back to "Use the default SharePoint form" and then you will see a "Delete custom form" option. That you can click on and remove the custom form so you can start all over.

Try that and then after deleted, click on the Customize in PowerApps again and it should generate a new "clean" app.
And, by the way, you are no bother - feel free to post and reach out as needed. I'd love to see you past the initial frustrations and well on your way to building some awesome PowerApps!