(currently appears in the Play Store as 'Email Blue Mail - Calendar')
(the images shown here are from version 18.104.22.168)
If this is the first time you have launched BlueMail, it will go automatically to the new account wizard. Otherwise, go to the Setting, Accounts and click Add Account.
From the first screen of the wizard, select Add Account.
When everything is correct, select Done.
#1 - ....your.domain.name is an example and not literal. Replace this with your own domain name.