As far as I know being a young earth creationist means that you literally believe that the earth was created ~6000 years ago in 6 24hr days by god. (six days of creation, 1 day of rest)
https://en.wikipedia.org/wiki/Young_Earth_creationism
you may be confused by old earth creationism, a form of creationism which isn't denying the evidence as much as YECs
https://en.wikipedia.org/wiki/Old_Earth_creationism