Open the crate several meters away from you, where you find broadhead arrows, over which you can climb, after you drive them into marked wooden surfaces. Right next to the fire, there is a spot where you can practice this.
Lara uses broadhead arrows automatically, after you aim at wooden surfaces. Shoot two arrows, one after another, but not directly next to each other. Safe zone around each arrow is marked by the white circle that appears while you are aiming. You need to try and shoot arrows in the way that makes the circle visible, at the moment of releasing the arrow. Otherwise, both of the arrows will get driven into the surface too close to each other. As soon as you manage to fix both arrows, jump up over them and zip down.
After a short climb, you will get to the camp, right next to the trader's cottage, who you have already had experience with. If you have enough money on you, take a look at the items he has on sale. Then, you need to climb again, using broadhead arrows, at the opposite side of the cottage.