Volunteers need to contact one of the registered groups/squads and ask to tag along. Unlike scenarios, where walkons are encouraged and herded to the right spot by CMs, there are no "accomodations" for walkons in FSO.
Doesn't mean ANYONE is excluded or uninvited, just that YOU need to take the initiative to ask one of the registered groups/spuads if they have an open seat and would be kind enough to have you (or, in the case of this thread, they advertise for some pilots). Once that is done, they add you to the roster, and you show up and know where to go and who to seek (your group).