Contact Management, located under the Site Management menu, is the sub-menu in which you are able to manage the Groups as well as the Contacts in each Group, which have both been generated by SignUp Forms.
1. Import Contacts
To add multiple email addresses to a group at once, go to Site Management > Contact Management > Import Contacts. At the top of the page, select the group that you want to import the emails into (1). You can also choose [New Group] which allows you to name a new group and import the contacts to that group. Then copy and paste the email adresses into the box provided (2) and make sure that they are separated by a comma or hard return (line break).