To add to what Paris Geek wrote:
1. You cannot do anything with Gmail labels via POP: i.e. you cannot have access to messages that have specific labels (aka folders in Aquamail). That is due to the limitation of POP3 protocol: it allows accessing only the INBOX.
2. For access to any other folders (representing Gmail labels) you should use IMAP type of connection (account in Aquamail).
3. For the instructions on how to access folders/labels in Aquamail, please read the answer to the Question "How do I access server side folders?" in the FAQ:
http://www.aqua-mail.com/?page_id=227And as Paris Geek wrote, you cannot create or delete a folder in Aquamail. You can only map those that already exist. But you can save or delete messages to/from the existing folders (labels).
Hope that helps.