This is the stone you found in the tunnel past the El Castillo inner pyramid
This is the scroll you found in the small chamber leading to the skull room
Number the rows on the scroll A to J and the columns 0 to 20 (1 being the first column of skulls).
Using the stone, work out on which row on the scroll each symbol appears:
Now work out the number associated with each symbol on the stone:
Put them together:
And read off the skull directions from the scroll: