You find the entrance to the tomb right after Lara spots the ship. Go towards the cavern exit and, in the spot shown in the screenshot, jump over to the other side. Walk over to the end and start the mechanism (to the right of the skeleton, there is a Document).
Past the mechanism, jump up and over the mast, walk over to towards the hanging lump of ice. At the end, run up (sprint), jump over the container and smash the ice lump at the other side. Thanks to this, you can now climb up.
You now need to give the turning wheel a turn. This lowers the container to the very bottom. Then, walk over the mast to reach its end (on the right), where you should jump onto the container, at the right moment, and smash the ice. After you come down, climb over the ice wall, on the left, and then climb even higher, from the spot, where there is the turning wheel.
Note: "The appropriate moment" is when the container is hanging for a moment at the same height as the mast and Lara on it. After you lower it and release the turning wheel, the container starts going up. You then have a moment to walk onto the mast and, when the container stops, you can jump onto it.
While up above, you find some coins, the Document and the Archivist map. Finally, examine the book that you find at the end of the path, in order to complete the tomb exploration.
Reward: "Ancient Skills" skill (enables you to fire two arrows in succession).