Fist things first, copy all the text in the spoiler.
Next, open minecraft and select "create new world"
Then click the world type generation box thingy until is says "customized".
Click the box and that appeared below it that says "customise"
then, there should be a box at the top of the screen full of letters and numbers. Delete everything in it and then paste the text you copied from the Original Post into it (ctrl v).
Click done. And create new world.