Login to your BlueHost account
Click on 'Domains' at the top menu
Click on the domain you would like to edit
Under 'DNS Zone Editor' click 'Manage'
To add Tracking CNAME enter the followng data. Click 'Add Record' when done.
Host = trk
TTL = leave as is
Type = CNAME
Points to = take this from your account. Go to application tab, click on the ESP you would like to associate with this domain, click on the '?' next to the Cname fieilds and copy the values.