Some of the Shrines require a special tool to access. This guide on Where To Find The Necessary Tool In Ghost Of Tsushima will tell you how to unlock the Grappling Hook, a special item that is required to climb to the summit of some of the Shrines and other areas in the game.
The Winding Mountain Shrine is one of many shrines scattered throughout the game world. If you explore this shrine early in your adventure you will be prompted with information pertaining to a specific tool that is required in order to ascend this Shrine to its summit. You cannot complete it without the Grappling Hook, which is the necessary tool the game informs you about when you reach the base of the shrine.
Where To Find The Necessary Tool In Ghost Of Tsushima
You must complete the story mission The Iron Hook. This is quite deep into the story of the first major territory. You have to aid with the Blacksmith, freeing him from captivity, help the Ronin straw hats with their plight, and complete most of the main story (yellow icon) missions in this area. Eventually you will have to meet up with the blacksmiths sister again. At this point, the leader of the Ronin Straw Hats will approach and ask for your help freeing menu from an enemy camp.
This is where the grappling hook is unlocked and the game uses it as a tutorial to tell you how it works. You jump and then press R2 to latch onto a nearby grapple point.