Customer Portal Ticket Customization

Customer Portal Ticket Customization

I'm trying to setup the ticket information in the customer portal and had a couple questions.
 
How do I customize what fields are available in the customer portal when the customer is submitting a ticket.
      For Example: Account Name
 
If I can edit this template can I associate contacts with multiple accounts and only those accounts show up in the drop down? Or are all the accounts in that department going to show up?