As you learn more about your contacts by collecting data about them, you learn how to better segment them into different groups. Creating more groups with better targeting will make your marketing more effective and save you messages, but you have to be able move them around to do that. Here's how.
How Do I Add & Remove Contacts to a Group?
Go to the Contacts tab.
Search for the specific contact(s) you want to move. Check the box next to the contact(s) to select them in order to move.
Above the contact, click on Manage Selected Contacts.
Choose Group you want to move or remove contacts from.
Choose either Add to Group or Remove to Group.