Add File associations for IOS in Xcode4

How to add a file association for certain extensions in xcode4. In the Xcode4/Target there is a "Document Types" section, i tried adding a few entries but i just don't get how to set this to open my files.

edit: Sorry if someone miss understood, what i really want is this: I'm developing an application for iPad, my users needs to upload a config file into the app, (a .conf开发者_Python百科), i wanna supply two ways to do so, trough iTunes "File Sharing", and Mail, ie, the user mail themselves the config, and in the Mail.app they touch the file and select "Open with..." and there they choose my app.

Document Interaction Programming Topics for iOS does a good job of describing what you need to do. Basically Info-plist information.

I would suggest a file suffix less generic than "conf".