where

Where is xxx?
問的是xxx"是"在那裏(意思是問地址/位置/座標/距離等客觀資料)

How to go to xxx?
問的是以"我"為主角"怎樣"走去xxx(意思是問方法/路線/方向等細節和指示)

We use "where" when we want to know the location of a place.
E.g. Where is (place)?

We use "how" when we want to know how to reach a place.
E.g. How can I get to (place)?

Example :

問 : Excuse me, do you know where is the xxx library?

(答)

問：How can I get there?

(答)