Hi Pam
within Email programs, Members is simply related to the leads that you have sent your email to them by creating that email program or the blast. And if any of those leads open the email or click a like inside your email them, then they CAN be considered as Engaged. So it’s up to you if you’d like to name them Engaged at this stage.
As Will mentioned above, "The Engaged Status is entirely determined by you. Its purpose is to catch and separate leads who have engaged with your email."
So if you and you managers would like to define Engaged status to those leads that opened the email and clicked at least on one email, then you would need a trigger campaign to change the value of their "Lead Status" field to "Engaged" based on triggers that fires when "click link on Email" or "Email opened" occurs.
Regards
Sepehr