Newbie questions: css path/selector

When I create css it just takes the one element, I wan't the whole path to be selected, for instance I may have set a specific class outside that element:

#top-nav-1 .nav-item

instead of just


When I press "create" it just takes that one element and, but it may be a setting I am missing. I watched a video on youtube and when he used create he also got the entire path it seemed.