i am starting in this of sync and I want to mark the points of the music so I now when to sync but i don't know the button for put the mark (a direct button to mark) so if you can tell me the button or how to do it I will be happy.
To set markers you use the astrix shortcut *
for more shortcuts go to help-> after effects shortcuts
press the . key or Control + . to start an audio only preview (set the length in preferences) then press Ctrl + 8 on a Mac or use the multiply (*) key on the number pad to set markers on the selected layer.
As an alternate, you can use Adobe Audition to find and set markers on an audio track, then when you save the audio track and bring it into After Effects the markers will already be there. Personally I use Audition most of the time to set cue markers in my audio tracks. It's faster for me to work that way and it's a lot more efficient way to find, name and adjust markers for audio. You can even do it with a video track.
There's a bunch you can do with Audio in Audition. Get started here: Audition for After Effects users