There are two opportunities to participate in FLOWS. These are either becoming a member of the Management committee (MC) or a member of one of the Working Groups (WG)
Management Committee member
If your country has accepted the Action's Memorandum of Understanding it is part of the Action and eligible of sending up to two delegates and up two substitutes to the MC. The MC meets regularly twice a year to take major decisions, review the status of the Action and determine future goals and direction of investigation.
FLOWS countries: http://www.cost.eu/domains_actions/essem/Actions/ES1301?parties
MC board of FLOWS: http://www.cost.eu/domains_actions/essem/Actions/ES1301?management
Become an MC member: http://www.cost.eu/participate/join_action
Working Group member
Members of the four WGs also meet regularly two times a year, typically in combination with MC meetings. These meetings are dedicated to address specific scientific topics of FLOWS and how they can be disseminated among a broader scientific audience and the general public.
Residents of FLOWS countries you can join WGs by sending an application to the leader of the WG (link) in question. The application should comprise a short statement of interest in FLOWS along with a wrap-up of your scientific background and a CV. Decisions will be made by the Core Group of FLOWS, which is currently formed by the chair, vice-chair, STSM manager and WG-leaders.