Item description:

Walk up to the HOS on right
(Cursor already on it - press X)

Press X again to continue
(To close the Instructions)

Reidso's Note:

** View Screenshot For Solution **
I did the Blue circled items first
Red circled items are either multi-step or a morphing item
which turns from a pebble to something else, then back again
**Remember to pick up the pebble revealed**

Reload my save if needed