Mark start position on accompaniment track

Multitracking. Having laid down the accompaniment track, I want to record a vocal on a 2nd track thyen up to three more tracks. I know I can listen through the headphones, but is there a way I can mark the accompaniment track to show where the vocal starts? Also, how do I align subsequent vocal tracks so as they start absolutely together. I know on ‘Mixpad’ you can do this and I find it’s very helpful. Thanks. John

In the Overdubbing instructions…
http://manual.audacityteam.org/o/man/tutorial_recording_multi_track_overdubs.html
…there are instructions for “tuning out” recording timing errors. If you do have errors in your overdub session, you can use the Time Shift Tool (two sideways black arrows) to push each track around so it matches. If your computer is powerful enough for overdubbing, it should be possible to permanently record new tracks in sync. If you have a wimpy computer with slow drives, then recording latency or sync may drift around.

You can create a Label “pointer” on any sound track and even put text into it to remind you why you did it.
http://manual.audacityteam.org/o/man/label_tracks.html

Koz