Hang from the ledge and make sure you are not hanging above a steam hole. Release to grab the horizontal pole below...

... then the next two poles. Lara will grab the poles with one hand, so press the Interact button to save her.

While hanging from the third pole, traverse close to the tower and release to grab the lower ledge.

Wait for another ledge to come below and release to grab it. Then drop to the second tier.