I'm a new

Chances are its just the default text, on either the Hello World post or Sample Page, to find either of these go into your WordPress admin, then go to Posts you will see a list of posts, if Hello World is there, you can either click edit or delete depending if you just want to change the content or remove it entirely.

Likewise for the sample page, again within wp-admin go to Pages and do the same thing for Sample Page.