Steps to add MIME types for a domain in HELM 3.2.11:
[1] Login to the HELM control panel of your domain.
[2] Click on 'Domains' icon.
[3] Click on your domain name.
[4] Click on 'MIME Types' icon.
[5] Click on 'Add New' button and then enter Extension and content type; save it.
Thanks,
Mike