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If the channel is available in your region you can just add those channels on your device. Just like your smartphone accesses an “app store” to add new applications, your Roku streaming player accesses the Roku Channel Store to add new channels. Install the channel on Roku and the first time you run it you provide your login credentials.
Click here for more information on how to add the channel to your Roku streaming device: How to add apps to your Roku streaming device