Alliance email

How do I set the alliance email associated with the account to be the main email.
Ex: is the default but I’d like be the the default when creating an email within the account. 

Hi Scott, do you mean alias?
You can setup your aliases for the account under Tools > Account > Your account > Aliases.

Just add the aliases you have associated with your account, and when you compose a new message, all the aliases should be listed in the dropdown for “from:”.

Hope this helps,