Follow these steps:
1. Click on your account to expand the folders list.
2. You should see your new Sane folders appear in the folders list.
If the above doesn't work for you, try these steps:
1. Go to Tools menu, click IMAP Folders.
2. In the Folders list, click the Sane folder you want to subscribe to and click on the green (+) Subscribe button.
3. Now you should see new folders appear in the folder list.