The company information you see at the bottom of emails is drawn from the Administrator's user profile. If you are the Admin, click your email at the top right, then "Personal Profile". The company name and address information is from that screen.
If you have more than one User in the account, the company information can be taken from the "Contact Owner" profile. By default that is the Administrator, but some of our clients run two separate businesses or divisions within their ONTRAPORT account by specifying another user as the "Contact Owner" of some contacts. That User Profile then fills in the company name and address information at the bottom of every bulk email. We have a short slide snow of doing this at http://support.ontraport.com/entries/66385934-How-do-I-Use-ONTRAPORT-for-two-businesses