they should already be a member of the io group if they were a member of the yahoo group. is the io group the same name as the yahoo group? if they did not receive the confirmation email tell them to do a search in io for the name of the group. it should come up and they can click on it.
when they create their io account the groups that they are a member of should also populate in the list under the groups icon.
they should have to rejoin the io group
