Mailchimp makes it difficult to create a new audience, because they would rather you make changes to existing audiences (to cut down on their server usage). That doesn't really work for us, though, so in order to create a new audience, click "Audience dashboard" in the left-hand navigation, click the dropdown for the current audience, scroll all the way to the bottom, click "View audiences," and then click the "Create audience" button on the page it takes you to.
Click "Create audience" again in the warning it gives you, and then it will take you to the "Create Audience" page. Fill in Audience name (usually the same name as the campaign), “from” email address (same as the campaign), “from” name (same as the campaign), and then scroll to the bottom.
IMPORTANT - Change Notifications to go to reupdates@spu.edu (this will go to University Advancement), and check "One-by-one: Unsubscribe notifications as they happen." Then, once you hit save, you will be able to import the CSV you have received for the mailing list. If you received the mailing list as an Excel worksheet, you will need to export it from Excel as a CSV.
Once the CSV is imported, it will let you check the columns you want to import. The only ones you need are First Name, Last Name, and Email Address. Then, once the audience is done processing, you should be able to go back to your campaign and add your new audience in the "Edit recipients" area.