How do you bring up the MS Outlook 2007 Account Button when you have MS Exchange setup in outlook

How can I add the Email Account button so that I can switch my outgoing email account when I need to send an email to a recipient. We have email set up on exchange but we use Outlook as the client. I have a seperate PC I use from home but do not have exchange server set up and noticed I have the ability to send from one of 3 email accounts depending if the mail is going to a personal friend. and old client for old email account and new clients with a newer email account. Can this be done with the current setup we have. I have looked everywhere to be able to turn on the account button. If not what would we need to do to get that done. Thank you.