When you log in to your Loader account, click the 'list of data objects' link located in the file uploader. This will bring up a dialog box. Choose your app, then click on a data object that you would like to import or update.
Feel free to switch between various data objects. You can also study data objects for other apps.
It is important to note that the names of fields in the Loader list may differ from the titles of fields in your app. This is primarily due to the technical jargon used by apps. We recommend that you play-test your import with Loader to ensure that your data is imported correctly.