In their first login, if their email addresses are already registered by you, they will have an activation link that wants them to create their passwords.
After creating their new password they will be able to enter to the account.
Or, if they have the same email address in your Raklet account and in their social network accounts, they can log in via Facebook, Google or Linkedin accounts as well.
If they enter an email address which is not found in your Raklet account, they will be invited to be a member. They can apply for membership via your membership application form.