Well, this is how I understand it:
(sorry my english, but I think you could understand me :- )
bar 1, start of song with the drum pattern that is written
the % sign means that the bar is like the bar before it, so
bars 2,3,4 and 5 are the same as bar 1.
bar 6, the / sings means each pulse, 1,2,3 and 4, the fill is
marked in the 3rd slash (/) and an accent in the 4th slash,
so you must play a fill in pulse 3 accenting it in pulse 4
bar 7 and 8, here the drum part changes to a groove that is
2 bar long. the .//. symbols means that the 2 bars repeats,
is like % but with 2 (or more) bars repeating itself.
so, bars 9,10 11,12, are repetitions of bar 7,8
bar 13,14, theres a fill in bar 14, no accent, so the fill
resolves in the 1 of bar 15
bar 15. Notcie de SIGN near to the A mark.
Here begins the A part of the song AND is the SIGN (notice it)
Notice also that the bar begins with a repetition mark :
that means that you will play until another repetition end :
The groove keeps in 2 bar length. So you play from 15,16
to 25,26 the same groove.
bar 27,28, note de "2nd ending on D.S" this means that when you
repeat this bars from the SIGN you must play what is written,
in this case two accents in 3 and 4 of bar 28, but if is this
the first time you play it... nothing happens.
bar 29, here is the casilla 1 (dont know the english term) that
goes from bar 29 to 32, so this means that the first time you must
play the bars as written from 29 to 32.
In bar 32 is the end repetition, so you jump to bar 15 where the
repetition begins
play from 15 to 26. So in bar 27,28 you play the accents
when you finish bar 28 accenting the 4, you move to casilla 2
in bar 33 (so you skip all casilla 1 bars 29 to 32)
You play casilla 2, from bar 33 to 46.
Notice the to CODA sign at end of bar 41 (skipt it for now)
Then you have the solos from bar 47 to the last bar 74
bar 74 you have a fill and then reads D.S al Coda
That means that you have to return to the SIGN in bar 15
and play again.
So you will go again through casilla 1, repeat from 15 again, and
start casilla 2
When you get to bar 41, instead of play bar 42 you go to the CODA
sign at bar 75 till fine in bar 77
Hope it works, sorry my english again.