If you enable Gmail Record Keeping in Top Producer, you can copy email you send/receive in Gmail to Top Producer. The email will then appear in the Activities tab in the Top Producer Contact Record for all those associated with the email. In order to do this, however, you must ensure that IMAP is enabled in your Gmail account.
For details on how to do this, refer to the Enabling IMAP article in the Gmail Help.
Note: If you do not want to copy email from Gmail to Top Producer, this step is not necessary.