Once installed (meaning that the ircam-antescofo folder is in your Max Packages folder), you should see an “Antescofo Tutorial” item in the Max EXTRA menu. Start from there.
I also strongly suggest you (and everyone) to switch to the just-released BETA version. It includes a new Antescofo Composer Tutorial, Part I: Boulez’ Antehemes 2 REMAKE. It includes a step-by-step reconstruction of an entire section of this famous piece with lots of useful pointers and information.
This BETA version also includes a brand new following algorithm that we’ve been testing in the past few months in various productions based on research by @cuvillier. It makes Antescofo extremely robust for regular repertoire pieces and readily useable for heavy Piano performances.
We are hoping to make the official release (v0.6) in November.
If you run into any problems with the this BETA version (v0.59) please post in Forum.