There can only be 1 Primary contact per account and you aren't able to assign another user to be the Primary contact from within the app. There are 2 options here:
1. You can change the username of the primary contact by logging in with that user and heading to PROFILE via the menu in the top-right. This will only work if the username that you're wanting to change it to does not already exist in our system.
2. If the email address that you'd like to be the primary contact is already a team member on the account and you just need the permissions changed, you can reach out to our support team at 888-493-2525 and we can change that over the phone. Please be prepared to validate the account with a recent invoice # or the last 4 digits of the credit card we have on file for you.
Let me know if you have any additional questions! Cheers!