How do I change the Salesforce Sync User?

The Salesforce sync user is the person the primary sync runs under. The primary sync is responsible for pulling data from Mailchimp and importing it into Salesforce. You can change this user, but you must be logged in as the user you wish to change to. Start by going to the Mailchimp settings tab and selecting General Settings. Click the icon next to the current user's name on the Salesforce Sync User.  A pop-up will appear that will confirm you are changing the Salesforce Sync User to your user.