I am having some trouble locating where I can add the "Join Our Mailing List" button to my campain? Also, is it possible to have the button open to a list that can be completed of contacts that would like to join as opposed to one by one? AND those contacts would then automatically be added to the list from which we sent the campain?
You can always take the link of your Constant Contact sign up form and add it into your email as a button, or link it to text. This way, the person can provide this link to all the members of the team that they want added, so they can all add themselves. I would suggest editing your sign up form first, as it looks like yours has not been edited since 2015. When you edit the form, you can select multiple list options for the members to add themselves on, or if you only provide one list option, they will automatically get added to that list. To access the link to put into your email, take a look at the image below: