Trying to learn how to use the sigh and fill

Asking for help with the icons on the side of the screen on your sign and fill. I was trying to use it and I don't know what I did wrong but I touched my page and it has lines on the page on paragraphs. And I try to clear it does not work. Also was wondering if you could use the keyboard for typing in the information before you sign. Cause it is hard to write legabale.