2 (simple) Questions: (background & login form)

Hi!

i have two (mayhaps easy) questions:

1. how can i make my background image stay here it is, and not scroll along with the page’s content?

my body code:

body{
	font-family: verdana;
	font-size: 95%;
	line-height: 115%;
	background-color: #1A1A1A;
	background-image: url(https://douglas-elemex.net/blog/wp-content/themes/elemex/images/back.jpg);
	background-repeat: repeat-y;
	background-position: center top;
	text-align: center;

}

2. how do i add the login form on the blog?

please excuse me for these questions, but i’m new to WordPress, and so far, it looks VERY promissing!

Thanks!