Any fields that are saved under contact information can be used as variables in your content (ie: name, address, etc).
To set a variable, click on My Account/Manage/Set Variables. Enter in the field you would like to use.
Click on Content/Edit Group/Edit your campaign/Preview/Edit to edit your content. Use the Variable drop down to enter in your variable.
When the campaign emails are sent, each contact’s email will contain the variables from their contact information.