You can change the Collection an audience belongs to from the Audience List Page or from Segmentation Center.
Changing the Collection from the Audience List Page:
1. From the dashboard, click the list icon and select Audiences to get to the Audience List Page
2. Click "View Details" next to the audience that you want to change.
3. Pencil edit the current collection to choose a new one.
4. Find the Collection that you want to move the audience to and click Move Audience.
Changing the Collection from Segmentation Center:
1. Navigate to Collections from the Segmentation Center and select the Audiences tab in the middle panel. Click the pencil edit icon next to the audience that you want to move.
2. Select the Collection to move your Audience to, and then select Move Audience.