。
She doesn't know how to ski.
Literal
She [topic-は] skiing [genitive-の] way [object-を] doesn't-know.
~の仕方 ('how to do X / way of doing X') is the noun-attaching version of the more grammar-ish ~方 (which attaches to verb stems, e.g., 食べ方). 仕方 itself means 'way / method / manner', and works with の after a noun: 料理の仕方 ('how to cook'), スキーの仕方 ('how to ski'). The polite negative 知りません ('do not know') uses 知る — a verb that takes ~ている in its affirmative form (知っている, 'know') but stays plain in the negative (知らない / 知りません). This asymmetry trips up many learners.