Just goto Settings and click the "Forwarding and POP/IMAP" tab and turn it on. If you don't see it, it will be there soon, as its being rolled out. Don't forget to click Save Changes when you're done.
I have already got this option.
Once you've enabled IMAP in your Gmail account, just configure your mail client or wireless device to download Gmail messages.
Supported IMAP Client List
- Outlook Express (Windows)
- Outlook 2003 (Windows)
- Outlook 2007 (Windows)
- Apple Mail
- Windows Mail
- Thunderbird 2.0
- For help accessing Gmail for mobile, please visit https://mail.google.com/support/bin/topic.py?topic=1580
* Palm handheld users: please note that Gmail IMAP access is not currently compatible with VersaMail.
So go there and get all Gmail synced in your Outlook or Windows Live Mail