...
To enable IMAP or POP open your Settings page and click the Forwarding and POP/IMAP tab. Scroll down to either POP or IMAP and click on enable.
Google also has a feature that will use POP3 to receive mail from up to 5 other email accounts. To enable it go to Accounts tab and locate the Get mail from other accounts section. Click Add a mail account you own and enter the email address. Enter the required information about the account and then click Add account. Since this uses POP3 when you check your inbox from the native address all of your mail will still be there unread, unsorted, and un deleted/archived.
Signature
In Gmail you can set a signature that will appear at the bottom of all your outgoing emails. This can be found in the Settings page under General settings. You can set your signature to anything you wish but typically it consists of your name, contact information and information about your title.
...