mrdanne You may wish to check out the tutorials here for background-positioning and background-repeat property which can guide you for setting the background image accordingly
Css specific property declarations :
Setting bg-image to center css property declaration:
background-position: center;
or background-position: 50% 0;
Setting bg-image to no-repeat css property declaration:
background-repeat: no-repeat;
however, there is even easier method for setting different properties in one declaration as given here
For providing the exact css reference declaration, Would require site link in order to review the same
Cheers