I have a lot of contacts. Can I turn on the Flexmls Portal for everyone at once?

Yes. From Contact Management, click the Advanced menu in the top right and then click Create Portal Accounts or Create Portal Accounts with Invite. The Create Portal Accounts with Invite option enables the portal for every contact and sends the default portal greeting as configured in Portal Preferences. The Create Portal Accounts option enables the portal for every contact, but does not send any notifications.