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Go to the Channels index page. Find the channel in question. Click the red link associated with the channel to arrive at the Edit Channel form.
On the Edit Channel page, note the current value in the path field. You should revert to that value after the distribution in question is complete.
Enter the temporary directory name in the path field, then click the Save button.
After clicking the Save button, you should be redirected to the Channels index page and you should see a confirmation message.
You can now perform a distribution. The files will be uploaded to the newly designated directory.
NB: Remember to revert the path field to its original value after the distribution is complete.