How do I put professional affiliations on a CV?
By 'Professional Affiliations' it is meant that one is a member of certain professional association such as IEEE, ACM, ICE, ASCE etc.

These professional bodies often arranges conferences which anyone can attend, so registering for the conferences does not mean that one is a member of a organizing body. Conference participation information may be put into your publication list as conference papers and/or given talks section.

So, You should only list the organisations as professional affiliations of which you are a member.