The format mentioned in the SDK docs says to submit a list like this:
contentID = "SOMEMOVIE1943"
mediaType = "movie"
contentID = "ANOTHERMOVIE1961"
mediaType = "movie"
....and so on...
I pasted my list into my channel's support info page and resubmitted the next update and then Roku used it to test deep linking. It's up to your code to see the contentID and mediaType being sent to your channel app and act accordingly. It's tricky to get the behavior right especially if you have subscription items, but there's a Roku app called Deep Link Tester that will help you get it right locally before submitting your channel and having it rejected after a 3 week wait.