Bluehost

From Shopify Wiki

You cannot add a CNAME record yourself, you need managed DNS to set a CNAME record at Bluehost.

Instructions provided at Bluehost:

"Bluehost Support Team will need to make any changes to your web sites’ DNS setting for “MX entries” that share the same priority, “A record”s or “CName”s. [...] Please request DNS changes by submitting a ticket at the helpdesk. To help expedite the process, please include your cPanel password or the last 4 digits of the credit card number inside the body of the ticket."

Alternatively,

1. Log into CPanel (at Bluehost! Shopify does NOT have a CPanel).

2. Click on Submit a Support Request.

3. Create ticket with your request.