|How do I add new information for each of my contacts?|
You could create a custom field to handle this.
Go to the 'Contact Lists' menu, choose 'Manage Custom Fields'.
Create your new field as a text field.
When you get to the last step, make sure you tick the right contact list for the promotion code to be 'attached' to.
You will then need to either:
a) Edit each contact and put the code in manually (this is ok if you have 5 contacts)
b) i) export your contacts email addresses
ii) edit the csv file in excel or a similar program
iii) add a new promotion code column and put a code per-contact in
iv) import your contacts again. Make sure you tick 'Update Existing Contacts'
This will ONLY affect the columns you have added to your import file. It will not touch any other data (eg 'first name').