How do I share an outing? On the outing, under "Who's planning this", type the person's email address. They must already use Helm: Revel finds them through Helm's own member lookup. If the address is not a Helm member, Revel tells you so, and nobody is invited, created or emailed — Revel sends no email and no invitations.
What shared people can do. Anyone on an outing may share it further. People on the outing vote on the candidate dates (each person votes only for themselves), say whether they are coming, and see who paid for what and who owes whom. An outing someone shared with you appears on your to-dos page under "Outings shared with me".
Removing someone, or leaving. Under "Who's planning this", the person who made the outing can take anyone else off it. Anyone else can take only themselves off — that is leaving the outing. The person who made the outing cannot be taken off it. When someone leaves, their votes go and a part they paid for no longer shows a payer.
Outings you are not on. You can only see outings you planned or that were shared with you. Ask whoever planned an outing to share it with you.