Follow the linear path along Coastal Bluffs. On the way you'll have to walk over a collapsed tree, but there's nothing to worry about; the sequence is pre-arranged and doesn't require any involvement on your part.
You shouldn't have any trouble jumping across a chasm a few steps later, either. Continue forward until you reach a wreckage of a plane hanging above a precipice.
Approach the wreckage and stand as indicated. Run and jump to grab onto the edge. Be ready to quickly press the action button to prevent Lara from falling.
Make your way towards the tail; you'll have to jump and grab another edge of the plane.
Get a grip on the top edge and move right. Expect to perform a new jump by pressing the action button again. The wreckage will soon fall into the precipice, but Lara will safely land on the ledge (reward: 100 XP).
Move forward, but be cautious around the edge of the cliff. After reaching the wall, follow the displayed tip. You'll have to press the jump button twice - first to bounce off the ground, then to bounce off the wall in order to reach the upper ledge.
Move ahead and jump down; you'll reach a deserted camp. That's where Lara will find a Two-way Radio.