Adding Creality touchscreen, build dimensions

I dont know much about this stuff. I tried the builder thing, I could not get anything to work. There is no build plate dimensioning, mine is 400x400x500. I also have the 4.2.7 board.
To add insult to injury, I have no idea what it is asking about referring to BL Touch, mesh or whatever, i just want 5 points.
I am soooo lost!
help please!