。
She showed the way to the post office on the map.
Literal
She [topic-は] that map [on-で] post-office [genitive-の] way [object-を] indicated.
示す ('to show, indicate, point out') is a formal verb common in academic writing, presentations, and physical pointing — broader than 見せる ('show by displaying') in that it covers indication and demonstration as well as visual presentation. で marks the means or instrument here ('on the map'). 郵便局 ('post office') retains a strong physical presence in Japan — 郵便局 (Japan Post) was a sprawling government institution until its 2007 privatization, and the iconic 〒 mark still appears on every postbox and post office sign across the country.