To manage the folders tap More (o o o) | Various Account Settings | Tap your Account | Folder Management | Folder Mapping.

To change the folder mapping, simply tap the folder you wish to map, and select the folder you wish to map to.

In general, your mapping should match the folders your provider’s web client is putting emails into.
This will help to ensure your sync is performed correctly. Emails you archive / delete / send in TypeApp will be placed in the correct location for later access on your Web Client and vice versa.

Note: Folder mapping is applied only to IMAP and Exchange and not for POP3.