The yellow X shows where you need to drop Lara in order to enter the doorway and continue with the level through the caves. The yellow dot shows where you need to go in order to take the shortcut.

Turn around and drop backwards to grab the edge. Release to drop to the slide. Press Action to grab the edge, as the screenshot shows. Instead of dropping next to the doorway, shimmy to the right and pull onto the flat ledge, where the yellow dot is.

Turn around and notice the Large Medi Pack below to the left. Walk up to the front left corner and take a running jump to the ledge next to the Medi Pack. Grab it and climb up the snowy blocks to find yourself close to the hut.