。
I slicked my hair back.
Literal
Hair [object-を] behind [to-に] smoothed-back.
髪の毛を後ろになでつける ('to smooth one's hair back') — なでつける is a compound: なでる ('to stroke') + つける ('to attach/apply'). The result is hair pressed flat against the head going backward. A simple grooming action described with a precise compound verb.