Export Email List to Excel/ Mailchimp

I have two separate email list that I need to have added to one excel spreadsheet. One list is on Cognito Forms and the other list is on my CRM. I also need the spreadsheet to be formatted so that I can easily export/add future clients to the fields without having duplicates. I then need the list added to Mailchimp. I dont know how to set up Mailchimp and i am looking for someone who can show me how to work it.