|Depends on the client.|
Are you trying to install a mail address with Outlook? There is usually a help guide in this.
Or are you trying to install a web based one like gmail or hotmail.
In my opinion, if you don't have a mail address, I would get a hotmail or gmail or yahoo account. The disadvantage of using an isp one, is if you change isp,
But you need to provide more details.
A thank you would be nice, if I have helped.